LIBRARY OF CONGRESS, 



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UNITED STATES OF AMERICA. 



THE PRINCIPLES 



Modern Dairy Practice 

FROM A 

BACTERIOLOGICAL POINT OF VIEW. 



BY 

GOSTA GROTENFELT, 

President Mustiala Agricultural College, Finland. 



Authorized American Edition 

BY 

I 

F. W. WOLL, 

Assistant Professor of Agricultural Chemistry, University of Wisconsin 



«»it!j illustrations. <^^o^co/u,^\ 

(SEP 7 1894 

FIRST EDITION. \^y„^ ^^r.\<t 



FIRST THOUSAND. 






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NEW YORK: 

JOHN WILEY & SONS, 
53 East Tenth Street. 

1894. 



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F. W. VVOLL. 



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\^ PREFACE TO AMERICAN EDITION. 



It is doubtful whether any industry has changed more 
during the past twenty years than has that of the produc- 
tion of milk and its manufacture into butter and cheese. 
Progress has been made in every direction. The present 
generation has seen the shallow-setting system of cream- 
raising superseded by the deep-setting systems, and these 
again largely by hand or power separators. The wonderful 
growth of the creamery movement, the invention of the 
cream-separator and the butter-extractor, the introduction 
of pure cultures in the manufacture of butter, have all 
come to us during this time, as have also the various 
methods of preserving milk for direct consumption; and 
still more, underlying it all, an increased knowledge has 
been gained and a fuller understanding of the nature and 
properties of dairy products and the changes to which they 
are subject. 

In this advance of the dairy industry the Scandinavian 
countries have taken the most prominent part, Denmark 
and Sweden having given the cream-separator to the 
world — the former country also contributing the method 
of ripening cream by means of pure cultures, and the 
latter the butter-extractor. Also Finland — Scandinavian 
by language, if not by government — has contributed her 
share to the advancement of dairying; and for a long time 



IV PREFACE TO AMERICAN EDITIOHT. 

past large quantities of " gilt-edged " butter have every 
year found their way from her distant borders to the large 
markets of the world. 

The author of this book is well known to Scandinavian 
dairymen from his numerous and important publications on 
dairy subjects; and in the broader field of science, whicli 
knows no boundary of nationality or language, his investi- 
gations relating to milk have made his name familiar to 
students of dairying and bacteriology. A study of the 
present work will, I think, show the reader that it is writ- 
ten by a thorough scholar, closely acquainted with all the 
different operations of the dairy. 

The work has been revised by the author at my sug- 
gestion, and several additions have been made — e.g., the 
whole of Part V, on " Cheese." It has been Yny effort in 
preparing the translation to make it directly applicable to 
our methods of dairying. It was therefore found necessary 
to edit the original in places to adapt it to the changed 
conditions. Numerous explanatory foot-notes and refer- 
ences have been added, which I trust will prove of value 
to the student of dairying and dairy bacteriology without 
detracting from the value of the book to the practical 
dairyman. I have endeavored to include all recent Ameri- 
can and European work in this line in my additions, so as 
to make the record of the investigations complete. 

I wish to acknowledge the assistance of Dr. H. L. 
Russell, Assistant Professor of Bacteriology of this Uni- 
versity, in preparing the translation. Dr. Russell has also 
kindly furnished me with several valuable additions giving 
the results of original investigations. 

F. W. WOLL. 

Madison, Wisconsin. 



TABLE OF CONTENTS. 



PAGE 

Introduction: Bacteria and their Relation to Dairying 1 



PART I— MILK. 

CHAPTER 

I. Milk as Drawn from the Udder 23 

II. Sources of Infection in the Stable, and its Prevention 26 

III. The Common Forms of Bacteria found in Cows' Milk . 80 

IV. Cleanliness in Butter and Cheese Factories 108 

V. Milk for City Consumption 137 

VI. Sterilization of Milk , . 144 

VII. Pasteurization of Milk 157 

PART II.— CREAM. 

I. Cream Raised by Gravity Processes 160 

(a) The Old Shallow-Setting System 166 

(b) The Modern Systems of Gravity Creaming . . . 175 
II. Separator Cream 181 

PART III.— SKIM MILK 

(a) Skim-milk from Gravity Creaming ........ 193 

{h) Separator Skim-milk 196 

(c) Pasteurization of Skim milk 196 

V 



VI TABLE OF COXTENTS. 



PART IV.— BUTTER. 

CHAPTER PAGE 

I. Trcalmcnt of Cream Previous to tlie Clmrning . . . . 204 

(a) Sweet-cream Butter. " Paris Butter " 305 

(h) Sour-cream Butter 207 

(c) The Use of Pure culture Acid Starters 220 

II. Maiiufactuie and liandliug of Butter 237 

III. Diseases of Butter 252 

PART v.— CHEESE 

I. Bacteria and Cheese-making 258 

II. Old-method Cheese-making 270 

III. New-method Cheese-making 274 

Index ,.,...... 279 



MODERN DAIRY PRACTICE. 



INTRODUCTION. 

BACTERIA AND THEIR RELATION TO DAIRYING. 

' ' Dairying is an art the success of which 
depends almost entirely on the extent to which 
■we succeed in controlling the various fermen- 
tation processes in their course." 

— Eknst Kramer. 

The great importance of bacteria in the dairy industry 
is at present admitted by all who have given the subject any 
thought. A knowledge of the nature and characteristics 
of these minute organisms will help us to understand more 
thoroughly the various manufacturing processes of the 
dairy and will throw light on problems that often perplex 
the dairyman. Since the changeable nature of dairy 
products makes it especially desirable to study all means 
at our disposal in order, if possible, to increase their keep- 
ing quality, an inquiry into the influence of the bacteria in 
the dairy will be of the highest value to the practical 
dairyman and to all who handle milk and milk products. 
It will teach us not only to produce goods that will keep 
well, but to care for them afterwards so that they do not 
prematurely spoil. 



2 MODERN DAIRY PRACTICE. 

Before proceeding to the consideration of these problems 
it will, however, be necessary to give some general informa- 
tion concerning bacteria and their prominent characteristics 
of life, so that the reader will be able to follow the discus- 
sions entered upon in the main part of this work. 

Bacteria. — Bacteria are the tiniest forms of organic life 
known; they are single cells belonging to the lowest type 
of plant life. 

They vary somewhat in form and there is considerable 
difference in size. The different species of bacteria cannot 
be distinguished by their form and shape as with the 
higher order of plant or animal life, because so many of 
them have such strong similarities in this respect. The 
usual method of classifying them, which is admitted to be 
imperfect, bases the distinguishing characters entirely upon 
shape. 

There are three fundamental types known, that may 
be compared in shape to a hall, a sliort rod, and a cork- 
screw. These three types are called (1) coccus, (2) ba- 
cillus, and (3) spirillum. All forms of bacteria may be 
referred to these three fundamental types, although there 
are gradations between them. Other names are given to 
certain species on account of the way in which the indi- 
vidual cells may be joined to each other: i.e., if the cell is 
isolated it is called a micrococcus ; two coccus forms Joined 
closely are spoken of as diplococcus. Sometimes the cells 
may adhere in long chains and are then known as strepto- 
coccus. If they form clusters instead of chains they are 
called stapliylococcus. A few coccus forms grow out in a 
platelike expansion, when they are called tetrads. If they 
multiply in three directions of space instead of in two 
they form cubical masses known as sarcina. 



BACTERIA AND THEIR RELATION TO DAIRYING. 3 

The hacilU include the elongated rodlike cells. They 
vary greatly in length and are sometimes divided into sub- 
divisions, such as bacterium, meaning a short cell devoid 









11 

Figs. 1-12. 






Fig. 1, micrococci ; Fig. 8. diplococci : Fig. 3, streptococci ; Fig. 4, tetrads ; 
Fig. .5. sarcina , Fig. 6. hncUli ; Fig. 7, comma bacilli ; Fig. 8, spirilli : Fig. 9, 
yeast fungi; Fijrs. 10 and 11, bacilli with spores ; Fig. 13, bacilli with cilia,— 
all highly magnified. 



4 MODERl!f DAIRY PRACTICE. 

of any spore-bodies within; bacillus, the normal rodlike 
type, reproducing by spores under certain conditions; and 
le^itothorix, where the filaments are extremely long and 
slender. 

The spirilla are the curved forms, and vary most in 
their outward appearance. They may be merely undulat- 
ing in appearance or in segments merely curved, when they 
are sometimes spoken of as vibrios. To this class belongs 
the cholera germ, often called the coinma bacillus on account 
of its curved appearance. Many times the spirilla are 
curved into several sharply-defined turns. 

Size and Weight of Bacteria. — As already mentioned 
the bacteria vary much in size, for which reason it is im- 
possible to give their average dimensions. A couple of 
examples will convey some idea of their extraordinary 
minuteness. 

A common lactic-acid bacterium is generally 3 micro- 
millimeters long and 1 micromillimeter wide. One micro- 
millimeter (yu) is yoVo millimeter or ^^^oo of one inch. 
How exceedingly small must not, then, the organisms be, 
25,000 of which may be placed side by side without span- 
nins: over more than an inch ! Not less than 10,000 million 
single bacteria would be needed to fill a cubic millimeter. 
Their weight is also exceedingly small. If we assume that 
the specific gravity of the bacterium mentioned is equal to 
that of the water (this may not be exact, but is not very 
much out of the way) it weighs a little over .0000000001 
milligram; and something over 900 billions of such or- 
ganisms are required to reach a weight of 1 gram {^^ of an 
ounce). 

Distribution of Bacteria. — It is evident that such small 
organisms may hide everywhere in nature. They have 



BACTERIA AKD THEIR RELATION TO DAIRYING. 5 

been found in air, soil, water, dust; on our clothes, on our 
skin; in the alimentary canal of man and animals, in our 
food; on the trees and the flowers, on the smallest as well 
as the largest animals, — in short, in almost every place on 
earth. Among the few exceptions to the omnijDresence of 
bacteria may be mentioned that they are never found in 
the uninjured animal and vegetable cells or in fresh, 
unwounded animal and vegetable organs. Their won- 
derful general distribution is due largely to their exceed- 
ingly small weight; they are easily carried around in the 
air, and when dry are moved by the least current. Certain 
bacteria furthermore possess power of locomotion in the 
fluids adapted to their development, and they can therefore 
spread in these substrata with wonderful rapidity. 

Multiplication of Bacteria. — The main reason of the 
universal presence of bacteria is, however, not to be found 
in any of the conditions mentioned, but in their enor- 
mously rapid reproductive capacity. This takes place 
partly by division, partly by spores. 

a. MuitipUcation by Division. — Bacteria may divide in 
different ways. The most common method is by the sim- 
ple division of a single cell-element into two equal parts 
{fission). This may continue in a linear direction, giving 
rise to long threads or chains of cells. In the case of coccus 
forms the continued division into twos may give rise to 
the streptococci {chain cocci) ; or, if irregular and in two 
planes, it may form flattened surfaces or bunches — pus 
bacteria. 

If division occurs in three planes we have the formation 
of the cubical masses or sarcina groups. 

Under favorable conditions the multiplication through 
division may take place very rapidly. It has been observed 



6 MODERN DAIRY PRACTICE. 

in case of some bacteria that the time elapsing between the 
division of the mother bacterium and the moment when 
the new bacterium in its turn begins to multiply amounts 
to only twenty minutes. As a rule the interval may not 
be as short, but it often does not amount to more than 
about an hour. A bacterium which grows and divides 
into two organisms during this time may, under ideal con- 
ditions, within 34 hours be the ancestor of 16,777,214 or- 
ganisms. A sarcina which produces, e.g., eight new bac- 
teria in an hour by dividing in three directions, may after 
20 hours have an offspring so enormous that it is 1,111,- 
152,347 times larger than the number of human beings 
found on our planet ; the figure indicating the number of 
this progeny would contain nineteen ciphers ! 

As a corollary of this enormously rapid multiplication 
it follows that the bacteria in general must exist in nature 
under highly unfavorable conditions, as they would other- 
wise soon fill the whole earth and annihilate everything 
else living. 

5. Multiplication ly Spores. — The multiplication 
through spores (Pigs. 10-11) occurs in the manner that 
small round or egg-shaped bodies with a characteristic 
power of refraction are formed within the bacterium, and 
later on these grow to ordinary bacteria, under proper condi- 
tions of heat and moisture. The spores possess far greater 
power of resistance against drought, heat, cold, etc., than 
do the bacteria themselves. The fact that these often 
prove almost indistinguishable from the material to which 
they have once gained access depends in most instances 
on the fact that spores have been formed there. If, e.g., 
sporeless bacteria dry up, they die comparatively soon, 
within a day, or perhaps a week. If the conditions are 



BACTERIA AND THEIR RELATION TO DAIRYING. 7 

not too unfavorable, the spores, on the other hand, may 
often continue to live for years after the nutritive solution 
has died out. It must be noted, however, that there are 
exceptions to the rule in both cases. The spores are far 
less susceptible to changes in temperature than the bac- 
teria themselves. While, e. g., sporeless bacteria generally 
are killed under favorable conditions within about ten 
minutes, when exposed to a moist heat of 158°-176° F. 
(70°-80° C), the spores of several species survive after hav- 
ing been exposed even to live steam for hours. The spores 
of a certain potato bacillus can stand this treatment for 
almost six hours without succumbing. A large number 
of spores are not killed except by dry heat at 266°-284° F. 
(130°-140° C). We thus find among the spores of bacteria 
some of the most tenacious organisms in the vegetable or 
the animal world. 

Some bacteria (above all a large number of bacilli) are 
supplied with fine cilia (Fig. 12), and have under favorable 
external conditions a lively power of locomotion. 

Pathogenic and Non-pathogenic Bacteria. — Some bac- 
teria have become known and feared from their power of 
producing infectious diseases in the animal body. Owing 
to this fact, everything known by the name of bacteria 
has been the object of fear and suspicion to most peo- 
ple. This is, however, without any foundation. By far 
the larger number of bacteria are not disease-producing 
and are not injurious to the animal organism. Some of 
the harmless majority distinguish themselves by the fact 
that they call forth fermentation in all kinds of fermenta- 
ble fluids, while others, as far as known to modern science, 
are entirely indifferent. 

In these studies and investio^ations we shall first of all 



8 MODEKN DAIRY PRACTICE. 

consider the bacteria producing fermentations. For this 
reason the following short account of the conditions of 
life of bacteria holds good primarily in case of this 
group. 

Nutrition of Bacteria. — The bacteria are usually ex- 
ceedingly unpretentious in their demands for the good 
things of life, a fact which, of course, is one of the main 
reasons for their universal distribution in nature. The 
smallest quantities of organic matter are sufficient for 
their support ; and wherever they find such a substance 
which possesses the moisture and heat necessary for their 
development and a reaction favorable to their activity, 
they will grow and multiply there. 

The bacteria live on the ready-formed carbonaceous 
compounds of organic origin, and do not as a rule possess 
the ability to make use of carbonic acid. The different 
species of bacteria usually select different kinds of carbo- 
hydrates. Some thrive best when the nutritive solution 
contains grape-sugar ; others when it contains cane-sugar 
or milk-sugar, etc. Hence we find that the different 
nutritive substances often are contaminated with their 
own peculiar kinds of bacteria. Only a few bacteria are 
omnivorous and satisfied with almost any organic sub- 
stratum. 

The nitrogen in the nutritive substratum required by 
the bacteria may be obtained not only from organic sub- 
stances, but from certain inorganic materials, like nitric acid 
and ammonia compounds. The bacteria, however, usually 
prefer albuminoids. Very few bacteria can do entirely 
without nitrogeneous substances. The need of the dif- 
ferent species of nitrogen varies greatly. The bacteria 
living mainly on carbohydrates need only very minute 



BACTEBIA AKD THEIR RELATION TO DAIRYING. 9 

quantities of nitrogen for their development, while a 
high nitrogen content in the substratum is an absolute 
condition of life with others. As regards the need of 
bacteria of salts (mineral matter) they behave usually like 
ordinary fungi. It must be especially noted that alkali 
salts are very important for the nutrition of bacteria. 

Bacteria and Moisture. — Not only the chemical com- 
position of the substratum : but also the degree of moisture 
in the same is, as already mentioned, of importance for 
the development of bacteria. Organic life is inconceiva- 
ble without a certain content of moisture in the nutritive 
substratum. We saw above that sporeless bacteria die 
comparatively rapidly in the absence of moisture, while 
the spores, on the other hand, retain their power of life 
even a long time after the substratum is completely dried 
out. 

Bacteria and Heat. — Heat, this mighty spring in the ma- 
chinery of organic nature, is also of great impoi^ance for 
bacteria, although the various species have very different 
demands in this respect. It may be said in general that 
39° r. (4° C.) is the lowest temperature at which bacteria 
can multiply and grow. Below this temperature they fall 
into a torpor from which they are awakened only by in- 
creasing temperature. 

With most bacteria the torpor-like condition appears 
even before this temperature has been reached. Some 
species have been found in ocean water and in the 
soil, however, which can multiply even at 0°. While 
the development of bacteria is arrested by a low tem- 
perature, a large number of them are able to stand intense 
cold without being destroyed. The bacteria of splenic 
fever are said to live even after having been subjected to 



10 MODERN DAIRY PRACTICE. 

a cold of —166° F. ( — 110° C.) for an hour, a temperature 
which only few organisms can stand ; the cholera bacteria 
can stand a cold of 14°F. ( — 10° C.) for the same length of 
time without being destroyed; and typhus bacteria have 
been known to remain alive for 100 days frozen in the ice. 
A special account is given later on of the influence of cold 
on certain fermentation bacteria. 

It is, however, not only cold but also high heat which 
arrests the development and multiplication of bacteria. 
Temperatures between 39° and 122° F. (4° and 50° C.) are 
most favorable to their development. At 140°-158° F. (60°- 
70° C. ) their vegetative forms are usually killed, provided 
this temperature is allowed to act for a sufficiently long 
time, while the spores can stand a much higher heat. 
The optimum temperature, i.e., the most favorable tem- 
perature, for the development of the patliogenic bacteria 
(the disease bacteria) coincides nearly with the body tem- 
perature of animals; for the greater portion of the other 
bacteria and especially for the fermentation bacteria it is 
from 59°-77° F. (15°-25° C). There are, however, num- 
erous exceptions to these rules. There are thus, e.g., some 
soil and water bacteria which only develop at 122°-158° F. 
(50°-70° C). I have further found bacteria in milk that 
were not only alive but multiplied at 140°-149° F. (60°-65° 
C). At lower temperatures the development of these bac- 
teria was practically suspended. 

Chemical Reaction Necessary for Baetsria. — The develop- 
ment of bacteria also depends on the chemical reaction of 
the nutritive substratum. An alkaline or at least a neutral 
reaction is an essential condition for a large majority. 
Some few bacteria can, on the other hand, thrive in an 
acid substratum, (e.g., lactic-acid bacteria). An acid re- 



BACTERIA AND THEIR RELATION TO DAIRYING. 11 

action of the nutritive substratum is especially favorable to 
the development of the moulds. 

Finally, two factors must here be noted which have the 
greatest influence on bacterial life, viz., air and light. 

Bacteria and the Air. — A large number of bacteria are 
entirely dependent on the oxygen of the air, and perish if 
they do not have access to the same. These are called 
aerohic bacteria. On the other hand, oxygen acts as a 
poison, or at least as a narcotic, to other forms {ana- 
erobic bacteria). Some bacteria can further exist both 
in an atmosphere of oxygen and in its absence. Many of 
the latter organisms differ in behavior according to 
whether they have access to air or not. 

Bacteria and Light. — The large majority of bacteria 
like total darkness, and only a few thrive in direct light. 
Direct sunshine as a rule acts as a poison on all organisms 
included under the term bacteria; and if ordinary day- 
light is allowed to act on them for a sufficiently long time 
and with proper intensity, not only most of the vegetative 
forms but even their spores will be destroyed. Sunlight 
is therefore the most common, the cheapest, and the most 
effective means at our disposal of fighting the bacteria. 
Light exercises its power of destruction of bacteria on a 
large scale. In nature the destruction is most intense 
during the summer months, A putrefactive liquid, the 
condition of which, as is well known, is due to a fermen- 
tation brought about by bacteria, can even become sterile 
through the action of sunlight alone. The more generous 
the supply of air while the bacteria are exposed to the 
sunlight, the more rapidly they and their spores are 
destroyed. 

Bacteria and Disinfectants. — It must furthermore be 



12 MODERN DAIRY PRACTICE. 

stated as a characteristic of bacteria, as well as of all other 
living organisms, that they shun certain chemicals which 
either arrest their growth or entirely destroy them. These 
materials are called either disinfectants or antiseptics. 
Further information concerning the disinfectants especially 
adapted for use in dairy practice will be found later on in 
this work. 

Bacteriological Methods of Investigation. — We cannot 
here enter into a detailed account of bacteriological meth- 
ods of investigation. It may be proper, however, to explain 
briefly the nature and general characteristics of these 
methods, in order that the discussions entered upon in the 
body of this book may be more easily understood by per- 
sons not familiar with bacteriological science. Those in- 
tending to study in a more systematic manner the rela- 
tions dwelt on, are referred first of all to the splendid 
text-books: C. J. Salomonsen's " Bakteriologisk Teknik for 
Mediciner," published in 1889, and Hueppe's comprehen- 
sive work, " Die Methoden der Bakterienforschung," 1889. 
An interesting and plain presentation of the subject is 
given in the Swedish language in Prof. Curt Wallis' book, 
" Bakteriologi " (1888).* 

* The following is a list of the more important works on Bac- 
teriology in the English and German languages, besides those men- 
tioned above: 

Sternberg. Manual of Bacteriology. New York, 1893. 

Abbott. Principles of Bacteriology. Philadelphia, 1892. 

Frankel. Text-book of Bacteriology, tr. by Linsley. New 
York. 1891. 

MiGULA. Practical Bacteriology. London, 1893. 

Jorgensen. The Micro-Organisms of Fermentation. London, 
1893. 

WooDHEAD. Bacteria and their Products. London, 1892. 



BACTERIA AND THEIR RELATION TO DAIRYING. 13 

Three methods are generally used in the study of bac- 
teria, viz.: (a) microscopic examination] (b) culture of the 
bacteria on different nutritive substrata; and (c) inocula- 
tion experiments with animals. As we are here dealing 
especially with non-pathogenic bacteria, we shall only 
dwell on the first two methods, since inoculation is only 
used in the study of pathogenic bacteria. 

a. Microscopic Examination. — In applying the first 
method, a compound microscope is essential. This ought 
to magnify at least 500 times, and preferably more. With 
such an instrument the presence of bacteria can be directly 
proved in several liquids, as in case of slops from creamery- 
gutters, standing liquid-manure pools, etc. In other liq- 
uids and in mediums where the bacteria present either ap- 
pear in smaller numbers or are extremely small or are 
hidden by other bodies (as in the cream and milk) they 
cannot be observed in this easy manner. In such cases 
the bacteria must be stained, — an operation usually per- 
formed by means of different anilin colors, — and they will 
then appear plainly when seen through a microscope. 
Although this method in many instances will lead to im- 
portant observations, it seldom gives decisive results as 
regards the question of the characteristics of single species. 
The bacteria are extremely simple organisms, which offer 

Kramer. Die Bakteriologie in ihren Beziehung zur Landwirt- 

schaft, Wien, 1893. 
Freudenreich. Bakteriologie in der Milchwirtschaft. Basel, 

1893. 
GCnther. Bakteriologie. Leipzig, 1890. 
Conn. The Fermentations of Milk. Washington, 1892. 
Weigmann. Die Methoden der Milchcouseryirung. Bremen, 

1893. W. 



14 MODERN DAIRY PRACTICE. 

but few dissimilarities in their outward appearance. There 
are, e.g., a large number of species among the micrococci 
which appear entirely similar by examination with a micro- 
scope, but which show great differences in their effects and 
general behavior in one and the same substratum, and thus 
indicate beyond a doubt that they are in reality different 
species. It has therefore been found necessary to seek a 
more certain method of identification than the microscopic 
examination, and such a one has also been found in the 
culture method. 

5. Culture Method of Bacteria Investigation. — Bacteria 
can develop in several kinds of media, both liquid and 
solid. In the former they form all kinds of flocculent and 
sandy growths, while in the latter they grow into more or 
less characteristic isolated masses, technically called colo- 
nies. In the culture of bacteria for scientific objects French 
bacteriologists previously used mainly liquid substrata and 
German preferably solid ones. Both kinds are of late made 
use of by all bacteriologists. The liquid nutritive media dis- 
tinguish themselves by the fact that the conditions which 
they offer to the bacteria resemble those found in nature, 
and that all kinds of fermentations may be more easily 
observed in them; the solid substrata, on the other hand, 
iire the more convenient ones to use when the question of 
the specific growth of different species is studied. Among 
the liquid substrata used in bacterial investigations may be 
mentioned beef-broth, milk, malt-extract, sugar solutions 
prepared in different ways, and extracts of various fruits; 
among the solid nutrients, prepared potatoes and beef -tea, 
to which pepton and all kinds of gelatinizing substances 
have been added, as gelatine, agar-agar, etc. Coagulated 
blood-serum and soaked wheat-bread are also often used. 



BACTERIA AND THEIR REEATION TO DAIRYING. 15 

Sterilization of Culture Media. — When these nutritive 
media are used for the culture of bacteria they must be 
sterile, i.e., free from all living organisms, as the culture 
would otherwise be impure from bacteria found in the sub- 
stratum before the organism to be studied was seeded or 
inoculated in it. Sterilization is usually effected by heat- 
ing to such a temperature that both bacteria and their 
spores are killed. As we saw in the preceding, the vitality 
of different species of bacteria differs greatly : while some 
bacteria are killed at rather low temperatures, others re- 
quire a temperature considerably above the boiling-point. 
To be absolutely certain that all bacteria, and above all 
their spores, are destroyed, we should heat intensively for 
every sterilization. In some cases this is impossible, 
as many substrata cannot be heated very high without 
being changed in one way or another. In case of such 
nutritive substrata we must therefore make use of other 
methods of procedure. A lower heat acting for a longer 
time or repeatedly may, e.g., be applied. This last method 
{intermittent sterilization) has to be used, among other 
cases, in the sterilization of milk and its products. 

Intermittent Sterilization. — Having killed the vegeta- 
tive forms of the bacteria through a careful heating, the 
substratum is allowed to stand at ordinary temperature for 
some time, so that the spores, which of course retained their 
vitality, may develop into ordinary^bacteria; and these are 
then in their turn killed by a second heating. As all 
spores may not then have reached the vegetative stage, 
or as some new spores may have been formed during the 
interval, it is safest to repeat the operation one or more 
times, according to necessities in each case. To be entirely 
safe, the milk is never used until its sterility has been 



16 



MODERN DAIRY PRACTICE. 



ascertained by its being kept for some time at a tempera- 
ture favorable to the development of the spores possibly 
still remaining in it. 

Method of Sterilization. — Several different apparatus 
have been constructed for sterilization of nutritive media 
through heat. The steam sterilizing apparatus introduced 
into bacteriology by Koch and Gaffky is generally used 
in Northern laboratories.* If this is to be used for the 
sterilization of milk, e.g., the substratum must be exposed 
in the apparatus to a temperature of 212° F. (100° C.) for 
three quarters of an hour each time on three consecutive 
days. Other substrata require of course a different treat- 
ment in order that the sterilization may be successful. Milk 
may also be sterilized in a very short time by being 
heated under pressure at 248° F. (120° C.) in a Chamberland 




* The Arnold Steam-cooker, an ordinary domestic utensil in 
America, is admirably adapted for purposes of sterilization. (Fig. 
13). 

Water is poured into the pan (or 
reservoir), whence it passes slowly 
through three small apertures into the 
shallow copper vessel (generator) be- 
neath, becomes converted into steam, 
and rises through the funnel in the 
center to the sterilizing chamber above. 
Here it accumulates under moderate 
pressure at a temperature of 213° F. 
The excess of steam escapes about the 
cover, becomes imprisoned under the 
hood, and serves to form a steam jacket 
between the wall of the sterilizing 
chamber and the hood. As the steam 
Fig. 13. is forced down from above and meets 

the air it condenses and drips back into the reservoir.— W. 



STERILIZING CHAMBEP 




BACTEEIA AND THEIR RELATION TO DAIRYING. 17 

Steam Sterilizer. When this method is followed, the milk 
is, however, often brown colored 




15 16 17 

Figs. 14-17. 

Fig. 14.— Test-tube closed with a cotton plug and filled with gelatine. The 
inner surface of the tube, the cotton plug, and the gelatine are sterilized. 

Fig. 15. — Culture of a bacterium in a test-tube. The bacterium has formed 
a large colony on the surface of the gelatine, and a weak bacterial growth is 
shown in the inoculation-needle track "stick." 

Fig. 16. — Shows a culture which peptonizes (liquefies) the gelatine. A colony- 
is also in this case first formed on the surface of the substratum, but as the 
bacteria liquefied this it gradually sank into the liquid formed. At the stage 
shown in the cut the bacteria appear as a small precipitate, c, at the bottom of 
the funnel-shaped, liquefied gelatine. 

Fig. 17. — Shows a culture of bacteria which also liquefied the gelatine, but to 
a smaller extent than the one last mentioned. Before the liquefaction, short 
filaments grow out into the solid gelatine from the " stick." 



The sterilization of some substrata may be accomplished 
by filtration through clay, gypsum, porcelain, asbestos 



18 MODERN DAIRY PRACTICE. 

paper, layers of sand, and so on, all prepared especially for 
the purpose. These filters retain all solid particles found 
in the liquids, and consequently also the bacteria. This 
method of sterilization is not, however, applied as often as 
the one previously given. 

Methods of Examination. — The culture of the bacteria 
takes place in the laboratory in sterilized glass vessels of 
different shapes. Ordinary test-tubes or glass flasks are 
most commonly used; in either case the mouth of the ves- 
sel is closed by a sterilized cotton plug. This allows the air 
to pass in and out, but prevents bacteria from gaining 
access to the vessel from the outside. Sterilized gelatine 
plates, properly protected against infection from the bac- 
teria of the air, are also used. 

In the bacteriological examination of a liquid substance 
this is first examined through the microscope ; the different 
kinds of bacteria in the substance are then isolated. This 
is done according to the method invented by Koch: one 
or two drops of the liquid are introduced into a test-tube 
containing some gelatine which has previously been lique- 
fied by careful heating. The sample is shaken carefully 
and rapidly, so that the gelatine cannot congeal, and is 
then poured on a glass plate protected from infection of 
bacteria and allowed to solidify. By the thorough shaking 
the individual bacteria in the drops of the liquid are scat- 
tered in the gelatine, so that on the congelation of the 
latter they are fixed at different places in the same. If the 
plate be now kept under favorable conditions of tempera- 
ture, light, and moisture, each one of the single bacteria 
will multiply and form colonies of varying sizes, as a rule 
visible to the naked eye (see Fig. 18). 

If the sample does not contain such an abundance of 



BACTERIA AND THEIE RELATION TO DAIRYING. 



19 



bacteria that the colonies go over into one another, differ- 
ent nutritive substrata may be inoculated with a part of 
the different colonies, and pure cultures are in that way 
obtained of the various organisms; provided, however, that 
the whole process has been conducted with due care and 
dexterity. When the various species of bacteria found in 
the liquid have been isolated in this manner, they are 
grown in different substrata to study their manner of 
growth and effects. The determination of the bacterial 




Fig. 18. 

a, glass plate; 6, congealed gelatine, in which may be found all kinds of colo- 
nies; the colony at c liquefies the gelatine, the others do not. The ramified 
colonies consist of moulds, the others of bacteria. 

contents of water or milk is as a rule conducted according 
to the method here given. By this and other bacteriologi- 
cal operations it is, however, not enough to make only a 
single examination ; a number of control cultures must 
always be made. 

Unfortunately all bacteria cannot be isolated and 
grown in this easy manner; but the method. of procedure 
in other cases cannot here be explained in detail, and in- 
terested readers are referred to the text -books already 



20 MODERN DAIRY PRACTICE. 

mentioned concerning this point, as well as all details in 
bacteriological technic. 

Before concluding this short explanation of bacteriologi- 
cal methods of investigation I will state that a large num- 
ber of bacteriological studies — at least in their beginning 
— do not necessarily require for their execution a complete 
laboratory, equipped with expensive and delicate apparatus. 
A number of simple pieces of apparatus fit for sterilizing 
material for bacterial cultures at a high temperature, etc., 
may be found in almost any modern kitchen. This is of 
great importance, since the field of investigation cannot 
always be near laboratories. A large portion of the bac- 
teriological studies upon which this book is founded could 
not, in the nature of things, be made in a city laboratory, 
but were only made possible because a small so-called 
bacteriological hand-laboratory was amply sufficient for 
their pursuit. Thanks to this fact I have been able to 
conduct my investigations in the midst of the industries 
whose conditions I intended to study from a bacteriologi- 
cal point of view. 

As an illustration of the importance of bacteria in the 
dairy industry, I will report an event which strikingly 
shows how the dairy products on a farm may for a long 
time be entirely spoiled on account of infection from a 
single harmful species of bacteria. On the estate Duelund 
in Denmark, belonging to Hofjdgermester Frits, who is 
so well known in the Danish dairy world, the principles 
of rational dairying have been followed since the introduc- 
tion of the dairy movement into Denmark. High-grade 
Dutter to which premiums were often awarded has long^ 
been made on the estate. But about a year ago it suddenly 



BACTERIA AND THEIR RELATION TO DAIRYING. 21 

became impossible to produce first-class, fine-flavored butter 
in the dairy of the estate in spite of the fact that the butter- 
making was conducted with every possible care and ac- 
cording to the same method as before. 

The milk was evidently not diseased when drawn from 
the udder, but on standing for a time it invariably assumed 
a putrid smell and taste, which even reappeared in the 
butter made from the milk. The accident of course 
caused the loss of large sums of money to the owner, the 
product of butter from the estate being very large. The 
best dairy experts were consulted, but their directions were 
of no avail. It was then suspected that the cause of the 
evil was of a bacteriological nature, and Professor C. 0. 
Jensen, the bacteriologist at the Copenhagen experiment 
station, was called in to investigate the matter. After 
having carefully studied the case he ascertained that the 
rapid spoiling of the milk was caused by a single small 
bacterium which had infected all the places where the 
milk was handled. He showed that the small disastrous 
organism had spread not only over the barn, where it 
was even found on the udders of the cows, but also all 
over the dairy. He isolated the bacterium and made it 
the object of lengthy investigations. By introducing 
cultures of it into sterilized milk he brought about the 
same peculiar changes which characterized the diseased 
milk at Duelund. 

The organism which caused so much harm and loss 
proved, however, comparatively harmless, thanks to its 
poor power of resistance. It dies at as low a temperature 
as 149° F. (65° C), and besides may be killed by means of 
ordinary disinfectants. After a disinfection of barn and 



32 MODEEN DAIRY PRACTICE. 

dairy it soon disappeared from Duelund, and first-class 
butter could again be produced there. 

If energetic remedies for the eradication of this bac- 
terium had not been resorted to in time, and if it had not 
possessed such slight resisting properties, a milk epidemic 
might easily have spread far around from this "pest- 
house," which, in spite of our modern highly-lauded 
rational dairy industry, had formed at one of the most 
carefully-conducted dairies in the great dairy country of 
Denmark. 



PART I. 
MILK. 



"Sauberes Euter, reine Hose und Hand 
Briugeu zur Ehre den Melkerstand." 



Swiss Proverb. 



CHAPTER I. 
MILK AS DRAWN FROM THE UDDER. 

When the milk is drawn from the udder of a healthy 
cow it is germ-free or sterile. Lister, Meissner, Duolaux, 
and other scientists have shown that such milk will re- 
main unchanged for all time without any preservatives 
being added, if it is only carefully protected from all bac- 
terial infection. The original sterility of normal milk is 
due to the fact that the bacteria cannot gain access to the 
milk-glands from without as long as the udder is not 
injured in any way, and that the udder can only be in- 
fected by bacteria from within, from the different internal 
parts of the animal body, when these parts themselves are 
infected with bacteria, i.e., are not in their normal, healthy 
condition. 

It is a comparatively easy bacteriological experiment to 

23 



24 MODEKN DAIRY PRACTICE. 

show the original sterility of milk after the experience 
gathered by the above-given scientists. It is, however, 
necessary strictly to observe certain precautions. The 
udder and its environments must be carefully cleaned with 
soap and water, treated with corrosive sublimate solution 
and washed with boiled, rapidly cooled water. The milk- 
er's hands should be washed in ether and alcohol, then 
rinsed with sublimate solution, and carefully washed in 
boiled water. The milk is drawn into sterilized glass 
vessels. Good results are generally secured when these 
precautions are followed, and when the milking is done 
rapidly and with precision, preferably at some place away 
from the cow-stable and other places filled with micro- 
organisms.* 

* The difficulty which bacteriologists have often found in obtain- 
ing absolutely sterile milk, when it has been drawn under observa- 
tion of all possible precautions, is explained by the observation made 
by Lehmann, that bacteria found in the drop of milk at the opening 
of the teat are able to work their way into the milk-cistern, where 
they then multiply very rapidly, favored both by the high tempera- 
ture and the rich nutritive medium. At milking the bacteria in the 
milk-cistern will be largely washed out in the first portions of milk 
drawn, liut all are not removed until the milking has progressed for 
some time. Lehmann (17te Versammlung d. deut. Ver. f. offent. 
Oesundhdtspjlege) thus found that the first milk drawn (300 cubic 
centimeters, about 10 oz.) contained 50,000 to 100,000 bacteria per 
cubic centimeter, while the main quantity of the milk drawn con- 
tained 5000 bacteria per cc. on an average, and the last 300 cc. were 
almost or entirely free from bacteria. Schulz {Arch. f. Eyg., 14, 260) 
in the same way showed that the first portion of a milking contains 
a large number of bacteria, while the last portions of milk are sterile 
when proper precautions have been taken. See also Gernhardt, 
Quant. Spaltpilzunters. d. Milch, Inaug. Dissert. Univ. Jurjew, 
1893.— W. 



MILK AS DEAWN FROM THE UDDER, 35 

In investigations concerning the original sterility of the 
milk I have followed a somewhat different plan from the 
one given. When the udder has been cleaned I have 
drawn the milk by means of a sterilized silver milking- 
tube, kept carefully protected from infection till it is used. 
Following this method I have succeeded in obtaining good 
results, even when the experiment was made in the barn. 
Nearly all the samples of milk remained unchanged, al- 
though they were kept for several days in an incubator 
(thermostat) at a temperature of 86°-90° F. (30°-32° C). 
This speaks decidedly in favor of this simple method, which 
doubtless is to be preferred to the older one, as the milk in 
the latter is far more liable to infection. 

Since the milk when drawn from a sound udder is abso- 
lutely sterile and will keep, — i.e., does not contain any 
micro-organisms, — our efforts must be directed toward pro- 
tecting it from infection ia the handling and further manu- 
facture in the dairy and creamery. We shall see in the 
next chapter that infection of the milk by bacteria is 
inevitable, and shall learn the best means of protecting 
the milk and its products from the same. 



OHAPTEK II. 

SOURCES OF INFECTION IN THE STABLE, AND ITS 
PREVENTION. 

On its arrival at the dairy the milk is always more or 
less infected with bacteria, it being impossible to pro- 
tect it entirely from infection in practical dairying. This 
is apparent from the mere fact that it is not always possi- 
ble to keep the milk sterile even when all precautions of 
a scientific investigation are taken. Lister's experiments 
concerning the original sterility of milk form an interest- 
ing illustration of this matter ; although the greatest pre- 
cautions were taken, he obtained only a very few milk 
samples that would keep as long as the milking was done 
in the stable. If the milking, on the other hand, took place 
in the open air, the experiments were nearly always suc- 
cessful. It would therefore seem that the air in the cow- 
stable at the time of these experiments was so mixed witli 
bacteria that in spite of all care it proved almost impossi- 
ble for him to protect the milk from infection. 

It is therefore evident that the milk already in the 
barn must be highly infected with bacteria in its ordinary 
handling. It is, however, out of the question to introduce 
scientific, exact means of precautions in the practical work 
in the barn, in order to prevent all infection of the milk, 
as this would make the work too complicated and expen- 
sive, and some of the precautions that would have to be 

26 



SOUECES OF INFECTION IN THE STABLE. 27 

taken (e.g.), the application of corrosive sublimate) are 
furthermore dangerous. Milk as found in practical dairy- 
ing has therefore lost its ability to keep for an indefinite 
period of time, and the various bacteria contained in it are 
trying to change it in one way or another. Fortunately 
we are so situated that the milk does not need to be 
entirely germ-free (sterile) for the purposes for which it 
generally is used, a truth which practical experience has 
long ago taught us. Experience has also taught us that 
the better we succeed in preserving the original qualities 
of the milk before the process of manufacture begins, the 
finer will the products be, and above all the better will 
they keep. However intelligent and experienced a dairy- 
man may be, he cannot make first-class products from milk 
that has been carelessly handled. 

Since bacteria are found everywhere, some one may 
object that it cannot be worth the trouble to fight them. 
A fight against omnipresent and even invisible enemies 
must at any rate be hopeless. This reasoning is not, how- 
ever, justified ; for we do possess strong means of fighting 
the bacteria. In several kinds of manufacturing enter- 
prises it is already possible to limit and govern the activ- 
ities of the bacteria. As an example may be mentioned 
that the standpoint was long ago reached by the manu- 
facturers of beer that they no longer need fear being dis- 
turbed in the normal progress of their work through in- 
vasion of bacteria, but on the contrary may determine at 
will the kinds of yeast that are to start the fermentations 
desired. Not until after this was reached it was possible 
to make well-keeping and always uniform products in 
this industry — a goal toward which dairying, of course, 
also must aim. 



38 MODEKN DAIRY PRACTICE. 

While we cannot hope to make a raw product of abso- 
hite keeping qualities in dairying, we must try to make 
it keep as long as possible, i.e., we must protect the milk 
from being spoiled by bacteria by all means at our dis- 
posal. 

Precautions against Infection of Bacteria. — The pre- 
cautions used against infection of bacteria are of two 
kinds, — (1) such as aim at the protection of the milk from 
infection from ■witliout', and (2) such as aim to chech the 
development and multiplication of the micro-organisms 
already found in the milk. In practical work these two 
methods go hand in hand, however, for which reason we 
shall not here attempt a strict separation. 

Infection during Milking, — The milk is exposed to 
infection from the moment it is drawn from the udder. 
Being pressed out of the teats in a fine spray, it comes in 
contact with the air on a very large surface ; the air in 
the cow-stable, and especially under the udder region of 
the cow, is nearly always filled with such bacteria as are 
the feudal enemies, so to speak, of the milk. If the 
milking is done in the open air, e.g., in the pasture, the 
danger of infection is of course less. It can easily be 
shown by a bacteriological examination, however, that 
there is a danger also in this case. By the shaking to 
which the udder and the parts of the skin next to the 
same are subjected in milking, bacteria are always loosened 
in large numbers and infect the air and the milk. This 
is plainly shown by the following simple experiment: 

Of two sterilized culture-plates with nutritive gelatine, 
which had been freed from all bacterial life by steriliza- 
tion, one was placed five to six feet away from the milker 
and the cow, and the other directly under the udder. 



SOURCES OF INFECTION IN THE STABLE. 29 

next to the upper rim of the milk-pail. When the milk- 
ing began both plates were uncovered at the same time, 
so that the bacteria gained free access to the gelatine. 
After a moment both specimens were again covered at the 
same time. The bacteria were then allowed to develop in 
the gelatine for twenty-four hours or more, when they 
formed colonies; and it could be observed with the naked 
eye that a many times larger nurnber of bacteria fell into 
the dish placed under the belly of the cow than into the 
one placed farther away. 

If this experiment is made in a stable filled with cows, 
the infection arising from the body of the cows will be 
shown still more plainly, as the cows are then far more in- 
fected by bacteria than in the free air. It is important in 
experiments of this kind in the stable to place the dishes 
at the same height from the floor, as there is a considerable 
difference between the bacterial contents of the upper and 
lower layers of the atmosphere in a stable. If the direc- 
tions given are followed it will be found, as in my experi- 
ments, that although a goodly number of bacteria will fall 
into both plates, the sample placed under the udder will 
contain a much larger number of bacteria than the plate 
placed a little away from the cow. 

These experiments show the truth of the fact known 
long ago, but often overlooked, that it is very important to 
keep the skin of the cows as clean as possible. 

Importance of Proper Bedding. — The first point to ob- 
serve in this regard is to provide the cows with bedding of 
dry, clean straw. The cows are often left to lie in manure 
and other filth — a condition which nullifies all precautions 
taken later on. Remnants of manure, etc., may be seen by 
a microscope in the milk from cows taken fairly good care 



30 MODERN DAIRY PRACTICE, 

of.* What an abundance of such filth and of the bacteria 
always prolific in such environments must there not be 
found in the milk from stables where uncleanliness of this 
kind reigns supreme. 

Relation of Grain-raising to Cleanliness in the Stable. — 
In days gone by, when the production of grain was the 
most important system of agriculture practised, there was 
an abundant supply of straw on the farms, and plenty 
could be used as litter for the cows. The fact that the 
feeding was not as intense as now also made it easier to 
keep the cows clean. The feed consisted mainly of hay and 
straw, and produced a dry, only slightly offensive manure. 
Now, on the other hand, there is only a limited supply of 
straw on the farms, and the high feeding practised makes 
it considerably harder to keep the cows clean, as it makes 
the dung watery and of a very offensive smell. In our 
days, when the demands for cleanliness in the stable are 
becoming more and more strict, the farmer has there- 
fore greater difficulties to overcome in trying to fulfil 
these demands, at the same time as he often has lost the 
best remedy previously at his disposal to reach this end. 
The explanation of the above-mentioned fact that a large 
number of dung and food particles and other impurities 
may be found by a microscope even in strained milk from 
comparatively well-kept cow-stables, doubtless lies here. 
The danger to the keeping qualities of the milk from this 
source arises from the fact that these particles are carriers 
of a considerable number of bacteria. I have repeatedly 
observed that a large number of spore-bearing bacteria 

* See Gripeaberg and Grotenfelt : Illustrations of Cows' Milk, 
Cream, etc. (Afbildningar af komjolk, gradde m. m.), Helsingfors, 
1889, p. 11, Fig. Vila. 



SOURCES OF INFECTION IN THE STABLE. 31 

and free spores were found on the contaminating particles 
in milk fresli from the cow, while such ones did not appear 
to any appreciable extent in the milk itself. After some 
time the impurities showed a far smaller number of bac- 
teria than before, while the milk itself teemed with them; 
the milk may therefore be infected even from the impuri- 
ties introduced in the same. 

At the same time as I made these observations I found 
micro-organisms and spores outside of the milk of exactly 
the same kinds as those found on the impurities of the 
milk, viz., in the manure remnants which had had a chance 
to remain for a time in the warm and moist atmosphere of 
the stable, and thereby became the seat of a luxuriant bac- 
terial growth, and also in the dirt on the skin of the cows, 
where the bacteria may develop rapidly, greatly benefited 
by the animal heat and moisture. 

Impurities in the Milk. — As the impurities which get 
into the milk even during the milking itself play such an 
important part in the infection of bacteria, it is important 
to learn their origin. The microscopic examination gives 
a good indication of their origin. I have found the fol- 
lowing kinds of impurities in unstrained milk fresh from 
the cow : 

1. Manure-particles (numerous). 

2. Fodder-particles (which have not passed the aliment- 
ary canal of the animals). 

3. Molds and other fungi. 

4. Cow-hair (numerous). 

5. Particles of the skin. 

6. Human hair. 

7. Parts of insects. 

8. Dovv'n from birds. 



33 MODERN DAIRY PRACTICE. 

9. Small wooden pieces, shavings, and pieces of fir- 
leaves. 

10. Woollen threads. 

11. Linen threads. 

12. Soil-particles (rather frequent) and moss -particles. 

13. Fine threads (most likely cobwebs), etc. 

In these investigations I also found several impurities 
in the milk whose presence I was unable to explain, as, e.g., 
cheesy lumps, slimy substances with a firmer nucleus, shin- 
ing, fat-like bodies, fine floss and grains, and similar 
matters. As regards the liquid impurities appearing in 
the milk, it need hardly be mentioned that they cannot be 
detected by microscopic examination.* 

* The quantities of solid impurities in milk have been deter- 
mined by Renk {Milnchner Med. Wochenschr., 1891, Nos. 6 and 7; Cen- 
iralbl.f. Bad., 10, 193), Schulz {Arch. f. Hyg., 14, 260), Vogel {Ber. 
Oes. Verh. v. Niirnberg, 1891, 78), Uhl {Zeiischr.f. Hygiene, 12, 475), 
and Ostermayer {Inaug. Dissert. Univ. Halle, 1S91). Renk examined 
ninety samples of market milk and found the following average 
quantities of impurities (mainly dung particles) in the milk of the 
cities given. The fresh substance is calculated on basis of an 80-per- 
cent water-content of the impurities : 

Leipsic. Munich. Berlin. Halle a. S. 
Dry substance, milligrams per liter 3.8 9.0 10.3 14.9 
Fresh substance, " " " 19.0 45.0 51.3 74.6 

The maximum quantities of impurities were found in case of a 
sample of Halle milk, containing 372.5 milligrams of fresh impuri- 
ties per liter (nearly 6 grains per quart). 

Schulz determined the quantities of microscopic impurities in 
Wurzburg milk, as sold in the city (I), as bought in the country (II), 

and as milked into a glass jar (III) : 

I. n. m. 

Dry substance, milligrams per liter ,.... 3.0 1.7 2.3 

Fresh substance, " " " 15.1 8.6 11.5 

The milk in case of I and II was strained through a fine gauze 



SOUKCES OF IJSTFECTION IN THE STABLE. 33 

It is natural to suppose that a good many of the con- 
taminating particles mentioned above came into the milk 
through the litter used ; this may thus both indirectly and 
directly contribute to the infection of the milk. Proper 
litter must not only form a good bed and quickly absorb 
the liquids, but must also as far as possible be free from 
dust and all kinds of soil particles, fungi, etc. We often 
find litter in our stables, however, which does not come 
up to these requirements. I may mention as an example 
that in several places where the generally excellent peat 
dirt has been introduced they have neglected to remove its 
dust particles as directed. As a result I have found large 
quantities of humus and sphagnum particles in the milk 
from farms where this practice was followed. I have also 
found fungi of all kinds in the milk from a stable where 
the fodder and straw litter were impure and moldy owing 
to bad weather during the harvest. The milk from a farm 
where they used pine leaves as a litter was found very 
impure, especially from manure particles, an observation 
which would indicate that this material, which also for 
other reasons is undesirable, ought not to be used as litter 
on dairy-farms. The sample of milk mentioned last also 
contained large masses of molds. 

The Flooring of the Stable. — An improper floor may 
also be the cause of infection of the milk, as may appear 
from the fact that the sample of milk which proved most 
filled with soil particles in my investigations came from a 
farm where the floor in the stable consisted of bowlders 

strainer. Vogel found 13.9 milligrams dry impurities per liter of 
Nilrnberg milk, and Uhl found 19.7 milligrams per liter of Gies- 
sen milk (average results). — W. 



34 MODERN DAIRY PRACTICE. 

partly covered with clay. At the front feet of the cows 
this was usually dry as powder and dustlike, while in the 
back of the stall it was solid and moist. At milking the 
cows often stamp their front feet, and it is highly probable 
that the milk in this way became filled with soil particles. 

Cow Stalls. — A too long stall may indirectly be the 
cause of infection of the milk. The hindquarters of the 
cow will, under this condition, be soiled by the manure 
when she lies down. This is especially the case with the 
tail, to which particular attention must always be paid in 
cleaning the cows. The cow will often swing her tail dur- 
ing the milking, and if it is soiled, filth will of course be 
spread to all sides. I have found that the milk may in 
this manner be mixed with dirt of the most offensive kind. 
At a farm where the stalls were too short, and where there 
was no litter in the liquid-manure gutter, the cows' tails 
were always wet and dirty; when the cows lay down their 
tails lay in the gutters, which did not thoroughly drain 
ofE the liquid manure. Although the gutters were new 
holes and recesses had already formed in them, in which 
the urine and liquid manure remained and formed pools. 
By applying wooden shavings in the gutters the difficul- 
ties mentioned were later on avoided. The cows could 
then be kept clean, and the milk became as a consequence 
cleaner, and kept better than was previously the case. I 
have met with liquid-manure gutters of even worse defects 
than the ones described in a large number of stables in our 
country. 

On another farm, considered a dairy-farm par excellence, 
all the stalls were too short for the large fine cows, so 
that the hind quarters and the tails always lay in the low 



SOURCES OF INFECTION IN THE STABLE. 35 

gutter; the ndders of a number of the cows were also dirty. 
What made the matter still worse was the fact that the 
stalls were lower than the barn-yard outside, where the 
manure-heap was placed. As a consequence the liquid- 
manure gutter was always full of urine. Only a couple of 
months after the herd came in from pasture, these sad 
conditions had conquered all the efforts of the farm-hands 
to keep the animals clean to such an extent that the hind 
quarters and parts of the udders were covered with a thick 
manure-crust, and the tail formed one solid, sticky mass. 
How impure the milk from this farm must have been may 
easily be imagined. 1 cannot give any exact data to what 
extent it was mixed with impurities, as I was not able to 
examine it closely; but, judging from the large quantity of 
slime gathered in the separator bowl when the milk was 
separated, it was as one would expect from its antecedents. 
Conditions similar to those given above, although not 
carried to such an extreme, may be found on other of our 
" dairy farms " — i.e. , on farms where they try, at least in the 
stable, to maintain a high standard of cleanliness. What 
can then be expected of the cow-stables in the places where 
they do not try at all to follow the fundamental principle 
of modern dairying — strict cleanliness ? The poor ani- 
mals are kept in such places in undisturbed peace through- 
out the winter, uncarded and uncleaned; they are further- 
more often confined in darkness for several months, as the 
very small windows are often wholly snowed or frozen 
over. Cow-stables where such bad conditions exist are 
still found in many places; and still people wonder that 
the milk coming from these primitive stables is of poor 
quality, and that the products made from it do not keep 
well. 



36 MODERN DAIRY PRACTICE. 

We saw in the preceding what a microscopic examina- 
tion of such milk would reveal. It is perhaps not possible 
to express through exact figures how such milk compares 
with milk from well-conducted farms as regards the quan- 
tity of impurities which they contain, but by a very simple 
examination everybody possessing a microscope — a very 
cheap one will do — may satisfy himself that the difference 
is very large.* In the milk produced on farms where 
strict cleanliness is observed, the contaminating particles 
are not only far less numerous, but also of another 
kind than in the milk from poorly-kept stables. It may 
of course hajspen that considerable quantities of fodder 
particles may be found in the former kind of milk; but 
with a few exceptions these have not passed through the 
animals, and are therefore not so well suited to being hot- 
beds for the development of bacteria as the numerous 
manure particles in the latter kind of milk. The milk 
from a poorly-kept farm also contains a much larger num- 
ber of spores of bacteria than milk from a well-kept farm. 
In extreme cases it is possible to tell these two kinds of 
milk from one another without a microscopic examination, 
since the more viscous and slimy milk from poorly-kept 
farms will pass through a fine strainer much more slowly 
than milk produced on carefully-conducted farms. 

Importance of Keeping Cows Clean. — The importance 
of carefully carding, brushing, and cleaning the cows is 

* Reuk {Milncluier Med. Wochensclir. 1891, Nos. 6 and 7) fouud 
the following quantities of solid im purities in the milk from different 
farms around Halle,— viz., 2.9, 7.3, 7.5, 9.4, 17.9, 37.2 milligrams per 
liter (quart) of milk. He says that the high content of impurities in 
Halle milk is due to " insufficient inspection, the feeding of roots, 
and the use of peat for bedding."— W. 



SOURCES OF INFECTION IN THE STABLE. 37 

apparent from the investigations reported. If the skin is 
smooth and shining, even a little uncleanliness is easily 
discovered, besides which a cow well taken care of does not 
lose her hairs so often, and they are not so loose that they 
easily rub off during the milking.* In cleaning a cow we 
ought not to have our attention mainly directed to the 
upper parts of her body, as is usually the case; but her 
lower parts must first of all be kept properly cleaned, since 
it is from these parts that hair and other impurities prefer- 
ably fall into the milk. 

If the more tender lower parts of the cows cannot be 
carded, they must be brushed and washed so much the 
more frequently. The tenderness of these parts will, how- 
ever, disappear as the cow becomes accustomed to their be- 
ing cleaned. If these parts of the bodies of the animals are 
badly soiled, they can only be cleaned again with a good 
deal of trouble, through repeated moistening and washing 
with soap and water. If it becomes necessary to wash the 
udder it should be done rapidly, and the udder must then 
be well dried with a dry rag, as it will otherwise easily take 
cold if exposed to draught, etc. 

In summer-time the cleaning of the cows is often neg- 

* Aside from the purely bacteriological aspects of the question 
there is a no less important advantage in carding and brushing cows 
in the resulting increased feeling of well-being of the cows, which 
may find expression in a larger production of milk and fat. Dietzch 
(" Die Kuhmilch," p. 21) states that "it has been found by experi- 
ments that cows kept in a clean condition gave, on an average, 1 liter 
(quart) of milk daily more than the same cows in a dirty condition. 
Backhaus {Journal f. Landwirtscliaft, 41, 332-42) also found an ap- 
preciable increase in the milk-yield of cows on two different experi- 
ments. Cf. the German adage, Out geputst ist halb gefuttert (" Well 
cleaned is half fed "). — W. 



38 MODERN J)A1KY PRACTICE. 

lected in the belief that they keep themselves clean in the 
pasture. It is, however, easy to satisfy one's self that it is 
both useful and necessary even then to brush them occa- 
sionally. The udders and bellies of the cows are easily 
soiled by dust, dirt, and the like, which is fastened loosely 
in the skin, and by the milking shaken down into the 
milk. In this connection I want to tell our farmers 
that they ought not to think too much of the trouble of 
driving the cows from the pasture to some neighboring 
lake or stream to bathe, where any such is at hand. The 
cattle gain not a little in general health thereby, and their 
bodies, and above all the lower parts, in that way get a 
thorough washing. In our land, rich in lakes, such summer 
baths might be given the cattle much oftener than is now 
usually the case. 

Even if all due care is taken in regard to the cleaning 
of the cows it is always necessary just before the milking 
to give the udder and its surroundings a further brushing, 
to remove all dust and filth, which otherwise would fall 
into the milk. It will not do to excuse the neglect of this 
act of cleanliness by saying that the milk will be strained 
and the dirt thus be removed from it anyway. First, a large 
portion of the impurities is so finely divided that it is not 
arrested by the strainer; and, secondly, the short time elaps- 
ing between the milking and straining is often sufficiently 
long to allow large numbers of bacteria to be washed from 
the impurities and to begin multiplying in the milk. The 
udders must not remain wet, as in such cases bacteria and 
dirt would accompany drops of water which may fall down, 
and would infect the milk. The parts mentioned ought, 
on the other hand, to retain some moisture, as dust and 



SOURCES OF INFECTION IN THE STABLE. 39 

dirt particles possibly remaining will then not so easily be 
shaken down. 

Cleanliness in the Milker. — The milker must be aware 
of the fact that he may spoil the milk by untidiness and 
carelessness. He himself must be cleanly, should wear 
neat clothes and a clean apron. 

In what contrast to this, as it would seem, simple rule 
is not the manner in which our milkers usually appear in 
the cow-stable. It seems to have become almost a tradi- 
tion that the farm-hands may be dressed carelessly and 
slovenly while doing their work, and in most places the 
clothes are the same for all kinds of work done in the barn. 
They often go to the milking in the same costume and 
with the same unclean hands as to the cleaning of the 
stable. And we often see that the milkers as they get 
out of bed in the morning go unwashed and unkempt to 
the milking, dressed in the most ragged and dirty articles 
of clothes in their possession. It is certainly strange that 
such carelessness is allowed to pass unnoticed on most 
farms. 

In this connection attention may properly be called to 
the unfortunate condition that clothes especially used for 
the work in the barn in many places are kept day after day 
in the cow-stable; they are never aired or washed, — a fact 
which is but too plain from their offensive smell. It is 
almost impossible to calculate how much mischief such 
dirty articles of clothing may cause in regard to both the 
health of the milkers and the taste and keeping quality of 
the milk. Such " small matters " often give a clue to 
diseases of the milk, of which many complain without 
understanding their cause. One condition of getting rid 
of these diseases is therefore tliat the clothes of the milkers 



40 MODERN DAIRY PRACTICE. 

be made of wash-goods, and that they be often aired and 
washed. The milking is certainly so important that due 
attention ought to be paid to all circumstances in connec- 
tion with it. 

The observation of constant and strict cleanliness and 
the wearing of proper clothing on the part of the milkers 
would furthermore help to raise their moral and social 
standing. Here is not, however, the place to dwell on this 
side of the question, and I shall only call attention to the 
motto at the beginning of this part, which expresses what 
the Swiss think about this matter. 

Wash-water for Milkers' Hands. — The milker must 
be particularly careful to clean his hands previously to 
the milking. They may easily come in contact with the 
milk during the milking, and thus cause a direct in- 
fection. After having milked a cow he ought to care- 
fully rinse his hands in clean water.* I have found a 
bad practice in this line in many places — viz., that the 
water used for washing the hands is not changed; no 

* This may seem an unnecessary precaution to many, but at 
least in case of sick or diseased cows in a herd the direction given 
should be strictly followed. Nocard and Mollereau (see Bang, Re- 
port 14, Copenhagen experiment station, 1885, p. 15) have called 
attention to the fact that the milker may often be the cause of carry- 
ing contagion from one cow to another. They give the following 
experience: " A cow was sent to Paris by rail and as she came 
from the car she was milked by a milker from a neighboring stable, 
where inflammation of the udder for a long time had appeared. 
Hardly six weeks after she had been placed in a previously healthy 
herd it was noticed that her udder was caked; the milk became 
unsalable,- and the disease soon spread to the majority of the other 
cows in the stable. It was ascertained that the disease did not ap- 
pear in the stable from where the cow came." — W. 



SOUKCES OF INFECTION IN THE STABLE. 41 

matter how many the milkers and cows are, the same, and 
often scant supply of water has to do service for all through- 
out the milking. It is natural that bacteria in this way 
will accumulate in the water, and that the washing will do 
more harm than good. The practice which some persons 
have of dipping their fingers into the milk during the 
milking, in order to give them the desired degree of moist- 
ure, is nothing short of horrid. 

Milking with Wet Hands. — The milking ought in no 
case to be done with wet hands — a custom so common that 
we even sometimes hear it asserted that it is impossible to 
milk with dry hands. This is, however, not only possible, 
but far more, an absolute necessity. Milking with wet hands 
cannot be a clean operation, a Danish author says, and 
correctly; for even if the teats are wiped dry and cleaned 
in the most careful manner they are not so clean but that 
the hands of the milker, if wet, may be soiled by touching 
them. 

Manner of Milking. — The milking is with us usually 
done in the way that two fingers, or at best the whole hand, 
is made to press along the teats, and the milk is thus 
driven out of them. This method is, however, to be re- 
jected. The strong pulling on the teats is not agreeable 
to the cows, and may even give rise to cracking and dis- 
eases of the udder. The milk is not formed in the teats, 
and the elaboration of the milk is not therefore forwarded 
by stretching them. Only by a deliberate and quiet press- 
ure of the milk out of the teats and an irritation of the 
lower part of the udder can a complete clean-milking be 
obtained, and at the same time the secretion of milk will be 
promoted. The method of milking common with us ought 
to be rejected for the further reason that it contributes 



43 MOt)ERN" DAIRY PRACTICE. 

greatly to the infection of the milk. As the fingers rub 
down along the teats they loosen and pull into the milk 
all the dirt which was not removed by the washing of the 
udder. The hands of the milker furthermore often come 
in contact with the milk by the strong pulling of the teats, 
and dirt adhering to the hand may thus be washed into 
the milk-pail. If dairy products of the highest quality are 
wanted, this method of milking must therefore be done 
away with, and the milking performed in a way similar to 
the following given by a Danish writer : 

" Take hold of the udder with the whole hand, so that 
the small finger will be held just so low that the stream of 
milk coming from the teat cannot wet the finger or the 
lower part of the hand. The hand is then lifted, opening 
it at the same time so that it takes hold of the teat very 
loosely, with a quick but soft pressure, and is then lowered 
so far that the teat is stretched Just to its natural length. 
At the same time as the hand is brought downward, begin 
to press the teat from above downward, and end with 
squeezing the milk out with an increasing pressure of the 
whole hand. This pressure, with a soft push into the udder, 
is a splendid means of emptying the udder. The move- 
ments must not be violent, however, but soft and at the 
same time as energetic as possible. Finally, when only 
a little milk remains in the udder, the milking is continued 
in the same manner, only with the difference that the hand 
is entirely loosened from the teat every time it is carried up 
toward the udder, and the lower part of the udder is held 
by the thumb on one side and the other fingers on the 
other side ; the udder is then given a couple of soft pushes, 
and the milk pressed out in the manner given.*' 

The picture in the text, taken from Ugeskrift for Land- 



SOUECES OF INFECTION" IN THE STABLE. 43 

mdnd for 1890, from which the above quotation is taken, 
shows the proper position of the hand in milking. The 
milk ought to be pressed out of the udder in regular unin- 
terrupted streams, so that it may be exposed to infection for 
as short a time as possible, this being especially threaten- 




FiG. 19.— Proper Position of Hands in Milking. 

ing when a fluid comes in contact with the air on a large 
surface. 

The milker must always be quiet and deliberate in his 
movements in the stable, and on approaching a cow ought 
to speak gently to her. If the cow is disturbed by knocks 
and pushes, as is often the case, she becomes impatient and 
nervous during the milking. She moves from place to place. 



44 MODERN DAIRY PRACTICl!. 

shakes herself, and lifts her feet, movements which set 
legions of infections germs in motion in the immediate 
neighborhood of the milk. If the cow is restless during 
the milking the milk-pail may also easily be kicked over, 
and dirt and filthiness of all kinds may be thrown into the 
milk. Quiet and deliberate manners in the milker are 
therefore an advantage even in regard to the preservation 
of the original qualities of the milk to the largest extent 
possible. 

Usually the teats are moist after the milking is over 
on account of tlie irritation of the skin, splash, etc. If 
this moisture remains, something like a membrane is 
formed around the teat; colonies of bacteria quickly de- 
velop in this moist and warm membranous covering. The 
teats ought, therefore, to be wiped off after the milking is 
finished. 

Abnormal Milk. — The milker should closely observe the 
appearance of the milk during the milking, to see whether 
it is normal when drawn. If it has an unusual appearance 
it should by no means be mixed with the rest of the milk. 
AVe sometimes find that the milk from sick cows is bloody, 
filled with cheesy particles, or otherwise abnormally changed. 
When milkers meet with such milk they often quietly mix 
it in with the rest of the milk if its abnormal qualities are 
not very strongly marked. In this way large quantities of 
milk may be infected, and if the temperature is favorable 
for bacterial development, accidents may take place. If 
the milk, on the other hand, looks very bad they usually 
pour it out on the stable-floor. This method is of course 
objectionable. At many places this milk is fed to swine 
in the hope that these omnivorous animals are not so par- 
ticular and so receptive of contagion. It is doubtless a fact 



SOURCES OF INFECTION IN" THE STABLE, 45 

that cue of the reasons for the wide distribution of tuber- 
culosis may be sought here.* All abnormal milk ought to be 
removed from the stable and destroyed as soon as possible. 

Milk from Tuberculous Cows. — The most common form 
of diseased milk with us, which is abnormal when drawn 
from the udder, is that from tuberculous cows. Such milk 
should not be used without being freed from its infectious 
qualities, above all where tuberculosis of the udder is pres- 
ent. In the first stages of tuberculosis it is very hard to 
prove whether the milk has an abnormal composition or 
not without delicate bacteriological examinations; it still 
has the color and appearance of ordinary milk, and the 
number of tubercle bacilli in the same is comparatively 
small. But as the disease devel'^ps, the abnormal condi- 
tion of the milk can more easily be discovered with the 
naked eye. Even when the disease is in its earlier stages 
the milk assumes a somcAvhat yellowish color. Later on it 
grows thinner and less viscous, and a large number of 
slimy, cheese-like lumps may be discovered in the same. 
The color finally turns entirely yellowish brown. 

We are often able, even in the earlier stages of tubercu- 
losis, to tell the abnormal condition of the milk from the 
fact that such milk does not show an amphoteric reaction, 
but is alkaline — a feature which is of course the more char- 
acteristic the farther the disease has progressed.! 

* Bang states (Bull. 4, Copenhagen experiment station, 1885, 23) 
that at a Danish creamery where centrifuge slime was fed to swine, 
all of these proved tuberculous, and warns against the use of slime 
for this purpose without its being previously boiled or heated toward 
the temperature of boiling water. The prevalence of tuberculosis 
among swine in certain parts of Germany has been attributed to this 
system of feeding. (See Flihling's Landw. Zeiischrift 1893, p. 779 ; 
Milch-Zeitung, 1893, p. 673.)— W. 

f Amphoteric Reaction of Milk. — When drawn from the uddef 



46 MODERN DAIRY PRACTICE. 

According to Bang, tuberculous milk coagulates at 
75°-85° C, In regard to tuberculosis in cows, it may fur- 
ther be mentioned that not all glands in the udder are 
necessarily attacked by the disease at one time. The 
milk in the sound glands has in such cases been very rich 
in fat, and reminded one of cream in its appearance.* 

milk will as a rule turn red litmus paper blue and blue litmus paper 
red, i.e., give both an acid and an alkaline reaction. This double re- 
!ic\ion is explained by the presence of normal and acid alkaline phos- 
phates and carbonates in the milk (Soxhlet). On standing even for a 
short time, normal cows' milk has always an acid reaction. — W. 

* The subject of bovine tuberculosis has been much discussed of 
late among dairymen in all parts of the world, and its importance 
has hardly been overestimated. The complete eradication of the 
much-dreaded disease in our country is one of the great dairy prob- 
lems of the age. Fortunately we have in the Tuberculin test a 
ready and but rarely-failing means of discovering the disease even 
when it is in its early stages. Breeders of dairy stock are now be- 
ginning to sell their stock on a guarantee of freedom from tuber- 
culosis, as shown by the test, and dairy-farmers in buying new stock 
should insist on such a guarantee — in justice to themselves as well 
as to their customers. 

Dairymen suspecting tuberculous animals in their herds should 
not fail to isolate suspicious cases at once, and to call in a skilled and 
careful veterinarian to make the test. For a preliminary examina- 
tion of the cows the following schedule of manner of procedure 
adopted by Danish veterinarians may be of service (see Woodhead, 
" Bacteria and their Products," 1891, 235). 

a. "First of all the submaxillary glands are examined; these 
are easily felt, and any change is readily made out. 

b. " The glands at the root of the neck and those in front of the 
haunch bones are always carefully examined. The glands in the 
flunk should be equal in size— about the size of the middle finger, 
and not hard. Mere enlargement, however, even when considerable, 
is not looked upon as of great importance if it is perfectly equal 
on both sides. 

c. "The animal is made to cough by means of pressure on the 



SOUKCES OF INFECTION IN THE STABLE. 47 

Milk from Inflamed Udders. — Another form of diseased 
milk which is also abnormal when drawn is that produced 

windpipe, and the lungs are carefully examined during and after 
the coughing. The condition of the skin over the flanks is carefully 
ohserved ; it should in a healthy animal be ' loose,' like that of a 
dog, soft and pliable ; any adhesion, hardness, or harshness should 
be carefully noted. 

d. " The udder is carefully examined for inequality of size or for 
any induration. It is a somewhat curious fact that tuberculosis dis- 
ease usually affects the hind quarters of the udder, which becomes 
hard and knotty, but not painful ; while in acute inflammation of 
the udder the anterior quarters are quite as much affected as the 
posterior ; the pain is usually very acute, and the process is accom- 
panied by much more marked febrile symptoms. 

e. ' ' Then the glands above the udder, high up between the quar- 
ters, are most carefully examined. In cases of tubercular disease of 
the udder these glands are invariably affected, are unequal in size, 
and the large one, corresponding to the affected quarter, is usually 
considerably indurated. 

/. "Careful auscultation is carried out at least once a month, 
the fore foot of the side that is being examined being always well 
advanced. The normal expiration-sound lasts half as long as the 
normal inspiration, and if this rhythm is deviated from in anyway, a 
further and thorough examination of the lungs should always be 
made. 

ff. " The examination is continued still further if the slightest 
suspicion of tubercular disease is aroused by the above investigation. 
... In case of suspicion the milk from that animal should not be 
put into the milk-supply, but is either thrown out or, after being 
most thoroughly disinfected by prolonged boiling, is given to the 
pigs." 

Prof. Nocard, of Alfort Agricultural College, France, who has 
made a special study of this subject, in a recent publication gives the 
following directions for manner of procedure in case of the appear- 
ance of tuberculosis In a herd {L' Industrie Laitiere, 19 (1894), p. 144) : 

"The diagnosing power of tuberculin is at the present time ad- 
mitted by all authorities, By its application it is easy to prevent the 



48 MODERN DAIRY PRACTICE. 

by COWS suffering from inflammation of the udder — a dis- 
ease which is not transferable from cows to man, as tuber- 
spread of tuberculosis in cattle. la all cases where tuberculosis has 
been found or is suspected, all animals in the herd should be injected 
■with tuberculin ; and those giving the characteristic reaction must at 
once be separated from the sound ones, and a thorough disinfection 
of the stable must take place. It is not necessary to sacrifice the 
diseased cows immediately ; their milk may be utilized after 
HAVING BEEN BOILED, and they may be prepared for the butcher, 
so that the owner may realize as much as possible on them. The 
disease having been taken in its beginning — at least in case of the 
greater number of animals— they fatten easily, and the loss resulting 
from sacrificing them prematurely will thus be reduced to a mini- 
mum. Delivered to the butcher at the proper time their lesions will 
be insignificant. [Tubercle bacilli very rarely appear in the flesh of 
animals, and even if such should be the case the bacteria, according 
to the consensus of authorities on the subject, are easily killed by 
simply boiling. — W.] 

"The essential point to be observed in all cases is to remove the 
diseased animals from the healthy ones, and to exclude them merci- 
lessly from reproduction. If the young animals escape infection 
the renewal of the herd will not be endangered, and the void will be 
filled in the courae of a couple of years. When I have applied 
tuberculin injections I have always assured the owners that the 
young stock which proved healthy would remain so in the future 
provided they were separated from the diseased animals ; and ex- 
perience has always confirmed the correctness of this prevision. 

" It is only necessary to go over a herd once with the test, if the 
directions given have been strictly followed ; no new animals should 
be introduced into the herd before having been subjected to the 
tuberculin test. 

" Thanks to this simple method, the owners of the animals 
can with little expense and without relying on governmental aid, 
free themselves from the heavy tribute annually paid to tuber- 
culosis. 

"Everybody knows, but it is well to repeat it, how dangerous 



SOURCES OF INFECTION" IN THE STABLE. 49 

cnlosis, but, to make up for it, is the more contagious for 
cows. As in case of tuberculosis it is caused by bacteria, 
and has frequently been the cause of large losses. We 
may here only recall the great damage which it caused 
in Holstein, 1873-78, where, e.g., at the estate " Stendorf " 
the whole herd of 200 milch-cows was attacked. As an 
example of the extremely contagious nature of the inflam- 
mation of the udder, the following may be cited : During 
the epidemic mentioned, the dairyman at Stendorf was 
once called to a remote farm where inflammation of the 
udder had never yet appeared, in order to assist in a hard 
parturition case of a cow. Six days after his visit the first 
case of inflammation of the udder was observed at the 
latter place, and before long six of the nine cows on the 
farm were attacked. The dairyman had doubtless brought 
the bacterium causing the inflammation to this farm. 
Milk from cows attacked by this disease may be recog- 

tuberculosis is to human life. In banishing the disease from the 
cow stables we banish one of the causes of its spreading among the 
human race." 

The following publications contain the main contributions to 
our knowledge of tuberculosis in cattle in America : 

Mass. (Hatch) Experiment Station Bulletin No. 8, April, 1890. 

Maine Experiment Station Report 1890, pp. 59-64. 

Pennsylvania Experiment Station Bulletin No. 31, Oct. 1893. 

Virginia Experiment Station Bulletin No. 26, March 1893. 

Ottawa (Canada) Central Experimental Farm Bulletin No. 30. 

Cornell Experiment Station Bulletin No. 65, April, 1894. 

Wisconsin Experiment Station Bulletin No. 40, July, 1894. 

Report on Tuberculosis in Ontario (Bryce), Toronto, 1894. 

Veterinary Magazine, 1894, p. 13. 

Also, Annual Reports of Bureau of Animal Industry, U. S. Dept. 
of Agriculture, Washington, D. C. — W. 



50 MODERN DAIRY PRACTICE. 

nized among other ways by its appearance, it being thick, 
slimy, and mixed with lumps.* 

" Diseased Milk." — It is fortunately still rather seldom 
in this as well as other northern countries to find the milk 
which is in any way abnormal when drawn from the udder. 
Creameries troubled with " diseased milk " are, however, 
often mentioned in our agricultural literature, and cream- 
erymen usually account for the poor quality of the butter 
produced by this reason. Milk which is abnormal when 
drawn may occasionally appear also on our farms, but 
generally the diseases of the milk met with in our cream- 
eries and dairies have arisen because the milk has been 
subjected to a careless treatment after having been drawn. 
Many dairymen try to hide their own faults and careless- 
ness by speaking of diseased milk, in the same way as 
persons who do not understand their business generally 
lay the poor results obtained to faults in the material or 
the tools. 

Light in Cow-stables. — If the preceding directions of 
strict order and cleanliness during the milking process and 
in all manipulations on the farm are to be followed, it is 
absolutely necessary to have suflBcient light in the stables, 
especially during milking-time. Most of our stables leave, 
however, much to be wished for in this respect. This is 
true not only of the previously mentioned dark, prison-like 
cow-stables so often met with at our smaller farms, but also 
of many farms run in a rational manner. It is of great 
importance to have sufficient light in the cow-stable, not 
only for the reason that the larger number of bacteria, and 



* See Baug, "The Causes of luflammation of the Udder ia 
Cows," 14th Report, Copenhagen Experiment Station, 1889, 38 pp. 



SOUKCES OF INFECTIONS' IN THE STABLE. 51 

those most injurious to the dairy business, thrive best in 
darkness, as we shall refer to later on, but it is impossible 
to clean the cows properly and to conduct the milking 
properly in a dusky stable. The co.w-stable must be lib- 
erally supplied with clean windows, and in winter-time it 
must be so arranged that the stable slmll be sufficiently 
lighted morning and evening. If we step into one of our 
common cow-stables on a winter evening at milking-time, 
we shall often be surprised to note how the milkers have 
to grope around in darkness while they perform their im- 
portant work and handle a material so delicate and easily 
contaminated as is milk. Under such conditions it is not 
strange if part of the milk goes outside the milk-pail in- 
stead of into it, and that the cows are not always clean 
when the milking begins. It is therefore an absolutely 
necessary condition for the production of milk that will 
keep well that the light in the cow-stables be improved; 
every milker ought, furthermore, to be supplied with his 
own bright shining lantern. 

Air and Bacteria. — As already mentioned, the impure 
air in the stable is one of the main causes of bacterial in- 
fection of the milk before it leaves the stable. There is 
no difficulty in proving this bacteriologically. The fact is 
apparent from the experiments above given made in the 
stable and in the open air, concerning the bacterial infec- 
tion from the udder and its surroundings (p. 28). Hesse 
states in his account of the quantitative determination of 
the micro-organisms of the air, that he found not less than 
120 bacteria and molds in a liter (quart) of air in a common 
cow-stable, while the same quantity of air in a dusty school- 
room, from where the pupils were just hurrying out, con- 
tained only 80 such micro-organisms. It has been found 



53 MODEEN DAIRY PRACTICE. 

by scientific investigations that bacteria do not multiply in 
the air; they lack there the moisture so essential for their 
development. The air can therefore be filled with bac- 
teria only by the drying and subsequent reduction to a 
powder-like dust of fluids and other media where these 
organisms are found, the dust being later on set in motion 
by currents of the air. The bacteria of the air are thus 
closely connected with the dust, and appear most numerous 
in air where a good deal of dust is set in motion. When 
the air is not stirred, both bacteria and the dust will of 
course sink to the ground or the floor. It has been found 
that the air in a closed living-house, when left undisturbed 
will become free from bacteria, in one to two hours. 

During the hot season the outside air contains most 
bacteria, while during snowy winters it contains very few 
such in our climate. In the atmosphere of cities con- 
siderably more bacteria are usually found than in the air 
in the country. On high mountains and out on the sea 
far from land, or deep down into the earth, the air seems 
to be sterile. 

Importance of Pure Air. — It is evident that the air in a 
cow-stable must be highly infected with bacteria a large 
portion of the day, it being usually in strong motion and 
an enormous number of them being scattered at feeding- 
time. As the bacteria obey the law of gravitation they are 
of course, as we have seen, most numerous in the lower 
layers of the air, i.e., just where the milking takes place. 
The bacterial content of the atmosphere in a stable varies, 
however, greatly at different times of the day, as I have 
often had an opportunity of proving in my investigations. 
While a sterilized gelatine plate placed in the stable im- 
mediately after the feeding within two minutes became 



SOURCES OF IISTFECTIOK IN THE STABLE. 53 

seeded with innumerable bacteria, a similar plate placed 
at exactly the same spot two hours after the feeding and 
the cleaning in the stable was done, did not become greatly 
infected with bacteria during ten minutes' exposure. This 
shows plainly that it is possible to considerably decrease 
the infection of the milk through the air of the stable. It 
is only necessary for this purpose that chores which con- 
taminate the air be done with the greatest care, and not 
performed at the time of or shortly before milking. 

Time of Feeding. On many farms it is the custom to 
feed the cows directly before or during milking. The 
intention is to direct the attention of the cow away from 
the milking, or to induce her to stand quiet during 
the process. It is, however, apparent that it is not nat- 
ural for a cow to eat while she is being milked, from the 
fact that she stops eating when the calf begins sucking 
her, and that she never grazes in the pasture while the 
milking takes place. I do not believe that feeding imme- 
diately before or during the milking tends to keep the cow 
quiet. But even if the method should bring this about, it 
is nevertheless to be rejected. Feeding directly before or 
during the milking leads largely to a contamination of the 
milk, especially when the cows are fed coarse fodders.* 
Masses of dust with accompanying bacteria are set in mo- 
tion during the feeding. Hesse states that the air in the 
stable in his experiments contained so many bacteria and 
especially molds when the feeding took place that it v/as 
impossible to count them. In an instance where very 
rusty chaff and straw was fed in a stable I found the air 



* See also Weigmann and Zirn, on the source of bacteria in milk, 
Milch Zeitung, 22, (1893) 569; Exp. Sta. Record 5, p. 431.— W. 



54 MODERN DAIRY PRACTICE. 

almost filled with such micro-organisms. As might be 
predicted, it was easy to trace large quantities of them in 
the milk produced on this farm, where the milking and 
the feeding took place at the same time. The feeding in 
many places is also performed in a manner most favorable 
to the spreading of the dust, e.g., by being thrown down 
from the hay-mow through a chute.* 

We then see that the quality of the milk will be greatly 
lowered by exposure to the dust stirred up when the 
fodder is brought into the stable and fed to the cows. 
The most typical bacteria in this dust seem to be Bacillus 
suit His and non-peptonizing forms resembling it. The 
reason why these organisms are so common in the milk 
may doubtless be traced to this origin. 

It ought furthermore to be remembered that cows like 
to take a quiet siesta after their meals, during which 
digestion may be allowed to go on undisturbed. It is 
therefore of much importance that some time — at least 
1^ hours — go by after the feeding before the milking 
takes place. In this way the animals will be more at ease, 
and the danger from infection will be decreased. 

Regular Cleaning of the Stable. — A vicious practice 
followed on many farms, which is perhaps more fatal than 
the unfortunate arrangement of feeding just mentioned, 
is that the manure is cleaned out during or immediately 
before the milking. It is not difficult to see that in clean- 
ing out the stable a mass of small particles of dung will 

* Some feeds, such as turnips, cabbage, silage, etc., may fuitber- 
more be fed safely after milking, while if fed before or during milk- 
ing they will give their peculiar flavors to the milk. Complaints of 
certain feeds tainting the milk have doubtless in many cases come 
from an injudicious method of feeding. — W. 



SOURCES OF INFECTION IN THE STABLE. 55 

be spread around in the air and fall down on the cows, on 
the clothes and hands of the milkers, in the niilk-pails, 
etc. The fact that many of the worst enemies of the 
milk are included among the bacteria adhering to these 
particles makes the matter still worse. Within a short 
time some of them produce putrefactive fermentations in 
the milk, while others do not show their injurious effects 
until later on — viz., in the products of the milk. During 
their presence in the milk bacteria of the latter kind 
lie in a torpor-like inactivity, from which they do not 
awake until they find conditions more favorable to their 
growth ; they then obtain power to conquer other bacteria 
found in the same medium, and soon give rise to their 
special fermentations. It ought to be remembered that 
the longer the manure remains in the warm cow-stable, the 
richer it will be in bacteria, and above all in spores of 
bacteria, and therefore the sooner it is removed the better. 
On some well-conducted farms I have seen this rule ob- 
served so carefully that the manure has been carried away 
as soon as it falls to the floor, an arrangement which can 
be carried out cheaper than many persons think. If the 
principle taught cannot be so scrupulously followed, it is 
necessary to prevent as far as possible the infection eman- 
ating from this source by other precautions. The ma- 
nure should be removed from the stable several times 
during the day, and it must be arranged so that a suffi- 
ciently long time will elapse between this operation and 
the milking. 

Dangers of Infection from Fermenting Foods. — Another 
quite common condition on our farms which is deleterious 
to the quality of the milk is that fermenting or spoilt 
cattle-foods, etc., are kept in the stable or in its immediate 



'56 MODERN DAIRY PRACTICE. 

vicinity.* The milk may easily be infected with very in- 
jurious bacteria from such hotbeds of fermentation. 

Ventilation in the Stable. — As regards the air in the 
stable, it is of the greatest importance to avoid as much as 
possible everything that may tend to make it impure ; 
the air must be kept fresh and pure by means of an 
effectual and well-arranged system of ventilation. The 
stable ought to be aired after each milking, and the clean- 
ing of stable and feeding should not begin till after the 
milking. 

In order that the ventilation be effective it is, however, 
essential that the air outside of the barn be purer than 
that in it, which in many places is not the case. Gener- 
ally the surroundings of the cow-stable are not given the 
attention and careful inspection which they deserve. 

The fear that the animals be exposed to draught must 
not prevent the airing of the stable, for draught can very 
well be avoided if the ventilation be arranged in a proper 
manner. The ventilation-valves of the stable ought 
always to be open except when the temperature sinks be- 

* The general use of silage as a food for dairy cows among Amer- 
ican farmers makes this a most important point to us, which we 
cannot ailord to overlook. In building a silo mere convenience in 
handling the silage is too often thought of, to the exclusion of con- 
sidering the influence of the presence of a fermented cattle-food on 
the milk and its keeping quality. The silo is often huilt in a corner 
of the barn, and arranged so as to open directly to the stable, filling 
the stable air at all times with a strong silage odor. Silage, and 
especially corn silage, is one of the great adjuncts to modern Amer- 
ican dairy-farming, but it is essential that it be fed judiciously, in 
connection with some dry coarse fodders, hay, corn fodder, etc., and 
that the feeding take place after, and not directly before or during 
milking. — W. 



SOUECES OF INFECTION IN THE STABLE. 57 

low 50°. Stables as a rule are kej)t too warm; the high 
temperature is not only not beneficial to the cows, but on 
the other hand is highly favorable to bacteria, the de- 
velopment of which takes place with far more intensity at 
59°-68° than at 50°. By a proper system of ventilation 
air containing fewer bacteria will get into the stable, and 
the multiplication of the bacteria present will at the same 
time be delayed and decreased.* 

* To show more plainly that the demands made as regards the 
order of work in the stable are not impossible, the author gives a 
schedule for the day's work which is in conformity with the princi- 
ples laid down. The schedule is not applicable to our American 
conditions, and is given here mainly as a matter of curiosity to show 
the amount of work and what length of day's work the European 
farm-laborer is asked to perform. 
" 4 A.M. Feeding. Cleaning out stable. 

5 A.M. Cows watered. Stable aired. 

5.30 A.M. The udders of the cows are cleaned and the milking 
begins. 

7-8.30 A.M. Stable closed. 

8.30 A.M. Feeding. Cows cleaned and brushed. 

10-11.30 A.M. Stable closed. 

11.30 A.M. Cows watered. 

13 noon. The udders of the cows washed and the milking begins. 

1.30 P.M. Feeding. Cleaning out stable ; cows let out and 
stable aired. 

2.30-4 P.M. Stable closed ; bulls let out. 

4 P.M. Feeding. Cows cleaned and brushed. 

5.30 p. M. Cows watered ; stalls carefully cleaned and stable 
aired. 

6 P.M. The udders cleaned and the milking begins. 
7.30 P.M. Distributing night-feed. 

8 P.M. Stable closed for the night. 

In making the schedule of work given, I have followed these 
main principles : 



58 MODERN DAIRY PRACTICE. 

Delay in Removing Milk from Stable. — No matter how 
carefully the precautions given concerning the treatment 
of the milk are observed, the milk is always threatened 
with infection from many sources as long as it is in the 
stable. The fact that milk when drawn from the udder 
has a temperature highly favorable to the development of 
the bacteria, and that it is a splendid nutritive medium for 
the large majority of bacteria, makes the matter worse. 
It is plain therefore that the milk ought to be removed 
from the warm stable as soon as possible. On most farms 
in our country an entirely different practice is followed. 
When a cow has been milked or the milk-pail is full, the 
milk is poured into a large transportation-can, at the open- 
ing of which a strainer is placed. As this does not allow 
the milk to run through very quickly, and the opening of 
the can is usually comparatively small, the milk must be 
poured slowly from the pail. The milk is usually left in 
the can until the whole herd has been milked, and it 
is then removed from the warm, foul air in the stable. 
This manner of procedure is very deleterious to the quality 

1. The manure is to be cleaned out 1^ hours before milking-tinif 

2. The stable is aired every lime it is cleaned. 

3. The cows are watered before every milking. 

4. The feeding takes place at least H hours before milking. 

5. The cows have a rest of 1^ hours three limes a day, during 
which time the stable is closed. 

6. The cows are cleaned twice a day ; their udders and hind 
parts are washed before every milking. 

7. The cows are allowed to exercise during the warmest time of 
the day. 

If the feeding takes place even five times a day, the demands 
made in this respect may be satisfied. If the number of feeds is 
smaller, it is of course still easier to observe these principles." 



SOURCES OF INFECTION IN THE STABLE. 59 

of the milk. It is exposed to air filled with all kinds of 
contagious organisms, and is /eft to remain in the stable an 
hour or still longer; this is so much the worse since the 
transportation-can is often not perfectly clean. I am fully 
convinced that diseases of milk with us are most frequently 
caused by irrational methods of procedure like those 
mentioned. Fortunately it is very easy to change this 
method so that it becomes, if not perfect, at any rate 
far better. First of all, the milk must be removed from 
the stable as soon as possible. Further, the milk ought not 
to be strained in the stable, but in a separate room near by, 
where the air is pure and fresh, and where cleanliness is 
observed in the most scrupulous manner. Such a room 
ought to be found in connection with every cow stable. 
It must not be placed in the neighborhood of the manure- 
pile, and is to be provided with large windows, but may 
otherwise be built very plainly. It is a good plan to 
keep the basin for washing of hands in this room, so that 
this operation may be performed after each cow has been 
milked.* 

* Another reason why the setting or separation of milk should 
not be delayed more than necessary is that delay will cause a di- 
minished yield of butter from the milk, making the skim-milk richer 
in fat. This has been shown by a number of experimenters : 

(1) Fm' creaming by gravity processes : by Fjord, 14lh Report of 
Dairy Experiments, 1881, p. 24; Henry, Wis. Experiment Station Re- 
port 11. p. 21; Wing, Cornell Experiment Station Bulletin No. 29; 
Babcock, Wis. Experiment Station Report VIII., p. 82; Hills, Ver- 
mont Experiment Station Report f. 1890, p. 100; Robertson, Canada 
Experimental Farms, 1891, p. 89; Dean, Ontario Agricultural Col- 
ledge Report 1891, p. 181; 1892, p. 219. 

(2) For centrifugal creaming : by Fjord (loc. cit.) and by Adametz 
and Wilckens (Ldw. Jahrb. 21 (1892), p. 131; Exp. Sta. Rec. 3, p. 



60 MODERN DAIRY PRACTICE. 

Straining the Milk. — As soon as the milk is brought 
into this room it ought to be strained through a fine 
strainer. By straining the milk in a room with fresh and 
pure air, a strong infection of bacteria is not only avoided, 
but the advantage is also gained that the milk is aired in 
the best manner. The animal odor of milk as drawn from 
the udder, which is so unpleasant to many, will not disap- 
pear to an appreciable extent if the straining takes place 
in tlie stable wliere the air is foul; the odor may, on the 
contrary, often increase by the milk being kept there for 
any length of time. In the fresh air of the milk-room 
the animal odor would, however, largely disappear. 

The straining of the milk may cause germs of infection 
to be spread in the milk instead of removing them from 
the same — if, e.g., the strainer-cloth is not changed often 
enough, or if the wire strainer is not frequently cleaned. 
In such cases it will easily happen that the finest dust-like 
impurities remaining on the strainer are pressed downward 
by the milk running through, and that the bacteria found 
on the larger impurities are washed off. Actual trials 
have convinced me that this may happen and largely 
contribute to the infection of the milk. I spread some 
coarse soil strongly impregnated with bacteria on a fine 
strainer cloth and poured newly-separated milk contain- 
ing only a small number of bacteria over the same. The 

652). The latter investigators, as it would seem, erroneously ascribe 
the diminished yield of butter in case of delayed separation to the 
transportation, instead of to the delay in separation incident to the 
same. Fjord showed that in the ice-setting system transportation 
gave even somewhat better results than mere delay for the same 
length of time. Delay caused a greater decrease with the ice-setting 
system of cream-raising than with the separator.— W. 



SOURCES OF INFECTION IN THE STABLE. 61 

bacteria in the milk were previously studied and found 
to be different from the characteristic forms in the layer 
of soil. After the straining the milk showed an entirely 
different appearance under the microscope than before. 
It now teemed with the same kinds of bacteria as those 
found in the soil. In a sample taken after the straining 
had continued for some time their number had, however, 
greatly decreased, and soon the strained milk contained the 
same kinds of bacteria as the unstrained milk, which 
plainly showed that the soil particles had lost their high 
bacterial content. By a bacteriological analysis of the 
layer of soil this proved to be the case, as this now con- 
tained only a very small number of bacteria. The strained 
milk was therefore far richer in bacteria than before the 
straining, and the keeping qualities of the milk were de- 
creased by the straining process; We thus see that by 
carelessness in straining germs of infection may be scat- 
tered in the milk. The large impurities are removed 
from the milk in the straining, but the most dangerous 
components of these, the fermentation -starters themselves, 
are washed into the strained milk. 

It is therefore very important to change the strainer 
cloth often during the straining; or, if a metal strainer is 
used, the operation should be changed occasionally by al- 
lowing steam or hot water to pass through the strainer in 
the opposite direction. The more unclean the milk the 
more frequently the changing and cleaning process should 
take place. 

In my straining experiments it was also shown that the 
more violently the milk dropped on the strainer, the more 
the strained milk was mixed with fine soil-particles and 
cowhairs. The kind of strainer used also played an im- 



62 MODERN DAIRY PRACTICE. 

portant part in regard to the quality of the milk strained. 
Milk of highest purity was not obtained by straining the 
milk through a good linen strainer-cloth, or by applying 
a fine wire-gauze strainer, but by placing the linen cloth 
on the wire-gauze strainer and allowing the milk to 
pass through them both. By changing the former as 
often as need be, the washing-down of bacteria from the 
filth remaining on the strainer will be limited as much as 
possible. 

Hauling the Milk. — When the milk is strained it should 
as quickly as possible be removed to the dairy or creamery 
for further treatment. If the greatest care has been taken 
in cleaning the cans, in milking and other manipulations 
in the stable, the milk in the cans will be only slightly 
infected by bacteria. If the milk is left for a longer time 
in wholly or partly closed transportation-cans and allowed 
to retain its warm temperature, the fruits of all preceding 
efforts will be destroyed. The bacteria in the milk will 
in such case begin to multiply rapidly, and the milk 
will soon be as highly infected as if no precautions 
whatever had been taken in the stable. It is not yet 
possible at this stage to tell by test or smell that the 
bacteria have begun to start injurious fermentations in 
the milk; but the results will be felt in the manufacture of 
the milk. 

If the creamery is near by the farm the milk ought at 
once to be hauled rapidly there, while in the opposite case 
it is necessary to take proper steps before the transporta- 
tion to check the growth of the bacteria. The best means 
at our service for this purpose is to cool the milk. 

Cooling the Milk. — If the cooling is conducted in the 
right way a strong current is started in the milk-can, so 



SOURCES OF INFECTION IN THE STABLE. 63 

that the last traces of animal odor may disappear,* pro- 
vided only that the can has not too small an opening. The 
cooling has, however, still more important results. If the 
temperature of the milk is lowered sufficiently, the de- 
velopment of bacteria will be completely stopped. The 
low temperature places these organisms in a torpid condi- 
tion, during which they are unable to multiply or to bring 
about fermentations. A proper cooling of the milk will 
therefore greatly increase its keeping quality. By lowering 
the temperature to 45*^ F. (7° C), satisfactory results may 
be obtained ; but it is safest in all cases to cool to a tempera- 
ture of 39" F. (4° C). 

If the milk is to be hauled to a creamery not too far 
away, where it will be immediately cooled further or 
separated, it is not necessary to cool below 50° F. (10" C). 
At this temperature the activity of the bacteria is generally 
stopped, and the small increase that may happen during 
the short interval will not cause any damage worth men- 
tioning, especially if the milk is protected from being 
heated during the transportation. Even a cooling to about 
54° F. (13° C.) has often proved of great advantage. 

The matter will, however, stand differently if the milk 
has to be hauled far, and if it is not protected from heat- 
ing during the transportation. The cooling must then be 

* It has beea claimed that a simple aeration of the milk will have 
a beneficial effect on its keeping quality but this is erroneous, as 
shown by Cooke (Vermont Experiment Station Report 1892, p. 127) 
and Wing (Cornell Experiment Station Bulletin No. 39; Powell 
Aerator). Aeration with cooling, on the other hand, will increase 
the keeping quality of the milk; see Wing, loc. cit ; Plumb (Purdue 
Experiment Station Bulletin No. 44); Hills (Vermont Experiment 
Station Bulletin No. 27) ; Armsb}^ Waters, and Caldwell (Pennsyl- 
vania Experiment Station Bulletin No. 20). — W. 



64 



MODEEN DAIRY PRACTICE. 



considerably stronger. The most imiaortant point in the 
cooling of the milk is, however, that it should take jDlace 
as quickly as possible. The object of the cooling is only 
partly reached if the temperature of the milk is not 
rapidly lowered to the degree which has been found prefer- 
able under the conditions of transportation present. 

Coolers. — Several kinds of apparatus for the rapid cool- 
ing of milk are sold.* Lawrence's cooler is best known 
(Fig. 20). It seems to me, however, it exposes the milk 




Fig. 20. — Lawrence Cooler. 

too much to infection from the air, etc. In this respect 
Pfeiff's cooler (Fig. 21) offers greater safety, but it has the 

* The following coolers and aerators are the main ones on the 
American market: "Star Milk and Cream Cooler," "Champion 
Milk Cooler and Aerator," "Howard's Patent Milk Cooler," 
"Powell Aerator." Dealers in dairy supplies will doubtless be 
glad to quote prices and give any other information desired con- 
cerning these and other kinds offered for sale. 



SOURCES OF INFECTION IN THE STABLE. 



65 



disadvantage of being difficult to keep clean. The milk 
is cooled in tank.^ by means of crushed ice placed in the 
outside tank B. As shown in the figure the milk is run 
through pipes and between cooled tin surfaces, and runs 
into the transportation-can at the other end. Other 
coolers will be mentioned later on under "Pasteurization 
of Milk." 

It must be emphasized that the cooling in no way may 
take place in the stable, although it is stated in some text, 
books on dairying that this may very well be done. 

We must not forget, however, that the bacteria are not 




Fig. 21. — Ppeiff's Cooler. 

killed by a simple cooling of the milk. When they again 
come under favorable conditions they at once begin their 
activities. This fact every dairy and creamery man must 
always keep in mind during the continued treatment of 
the milk. If the milk is subjected to a process of manu- 
facture it must of course have the temperature most 
suited for the different manipulations, but when left to 
itself the milk should always be kept as cool as the condi- 
tions will permit. 



66 MODERN DAIRY PRACTICE. 

When to Cool the Milk. — Among our farmers and 
milk-dealers there is a general belief that cooling is neces- 
sary only during the hot season — an opinion to which I 
most emphatically take exception. It is possible during 
the cold season to haul the milk even to a somewhat 
distant creamery without previous cooling and keep it 
sweet; but the development of the bacteria will not be 
sufficiently checked by this method. The results do not 
appear at once, but are felt later on, as the products made 
from the milk will not keep well. 

A quick and efficient cooling of the milk is a strong 
remedy to regulate and counteract the development of 
the bacteria found in it. It is my opinion that high- 
grade dairy products can only be made on farms where 
sufficient quantities of ice are used in the handling of the 
milk. Fortunately for our country, nature has arranged 
matters so that ice, the most effective and practical means 
of cooling the milk, is offered in sufficient quantities and 
at a low cost to our dairymen. 

The Value of Ice to the Dairyman. — In this very con- 
dition lies, in my opinion, the secret of the fact that we in 
this country, far away from the markets of the world, can 
compete successfully in dairying with other countries 
more fortunately situated as regards location and many 
other conditions. For instance, the ice in Denmark is 
both expensive and poor, and cannot every year be ob- 
tained in anything like sufficient quantities. Our con- 
ditions are entirely different. Our numerous lakes and 
streams yield ice in abundance. The hauling of it does 
not come high, and the quality of the ice leaves nothing 
to be wished for. Crystal-clear lake ice, more than two feet 
thick, of such purity that it leaves practically no sediment 



SOURCES OF INFECTION IN THE STABLE. 67 

on melting, is obtained here every winter. In Denmark, 
and still more in France and Ireland, which three coun- 
tries, besides Sweden, are our only competitors in the Eng- 
lish market, the dairymen are generally forced to cool the 
milk with water only — a method which doubtless is better 
than no cooling whatever, but which does not form any 
certain remedy against bacterial development. I have 
often had occasion to observe at Danish cooperative 
creameries that the milk even on arrival at the creamery 
has been somewhat sour or at least has been slightly off 
flavor, and that the butter when packed in the tubs has 
been soft and insipid — all a result of deficient cooling. 
More than once I have witnessed that the dairyman even 
on large Danish estates has been entirely at his wit's end 
for lack of means of cooling in the dairy. The Danes 
are fully aware of the importance of keeping the dairy 
products at a low temperature, but the only practical 
means which would make this possible — the ice — is often 
not to be had at a reasonable price. If we consider that 
ice-famines may as a consequence arise even at the large, 
financially strong proprietary creameries, it is evident that 
co-operative creameries cannot require their patrons to 
cool their milk immediately after the milking. The milk, 
which usually is hauled to the creamery only once a day, 
is at best cooled with water, but is oftener exposed to a 
very doubtful " air-cooling." The result is, of course, that 
a perceptible fermentation may often be discovered in the 
milk on its arrival at the creamery. And from a second- 
grade raw material no one can make high-grade products. 
One of the main reasons for the rather low price of Danish 
butter during certain seasons of the year must be sought 
in these conditions. 



68 MODERN DAIRY PRACTICE. 

Our dairymen and milkmen may draw many useful 
lessons from these facts. Ice can in our climate easily be 
kept packed in sawdust. Small milk producers who can- 
not make use of large quantities may join with one another 
in hauling and keeping the ice. 

Mixing Evening and Morning Milk. — In this connec- 
tion I will mention a mistake often made, viz., to mix the 
warm morning milk with the cold evening milk before 
the hauling. The whole quantity may be spoiled by this 
practice, as a temperature especially adapted to the growth 
of certain bacteria may under these conditions arise. If 
the comparatively warm, mixed milk be hauled a good 
distance to the creamery in the heat of the sun, it is not 
strange that it is changed on the arrival there, or at least 
contains a large number of bacteria the injurious effects of 
which it is hardly possible to overcome in the manu- 
facture of the products.* 

The milk ought of course to be protected against heat- 
ing during the transportation, a rule which is often 
violated. If it has to be transported a long distance, the 
milk ought to be cooled during the hauling, or ought 
otherwise to be pasteurized before shipping. (See under 
Pasteurization of Milk.) 

Care of Milk-pails. — A very common and strong in- 
fection of the milk which takes place both in the stable 
and the dairy is the one caused by carelessly-cleaned milk 
pails and cans. Even the first vessel which holds the 
milk when drawn from the udder, the milk-pail, usually 
leaves much to be wished for as far as cleanliness is con- 
cerned. At many farms in the old countries wooden pails 

*The churning of the milk which often takes place in hauling 
long distances is easily avoided by filling the cans completely. 



SOURCES OF INFECTION IN THE STABLE. 69 

are still used for milking. Such pails are, however, en- 
tirely unfit for this purpose, since all kinds of bacteria 
very easily lodge in them. By daily steaming, etc., it is 
certainly possible to prevent bacterial growth from gain- 
ing ground, but wooden vessels can hardly stand daily 
steamings; they will soon begin to leak. In case this cum- 
brous cleaning process is not carried on most carefully, 
irregularities will soon appear in the milk or its products 
pointing to a strong bacterial infection. It is therefore 
essential to use tin pails, which may easily be kept free 
from dirt with its accompanying bacteria. 

Even on well-kept farms the practice of leaving the 
milk-pails in the pasture is often met with in summer- 
time.* Instead of bringing them home to the dairy to be 
cleaned, they are rinsed in the pasture in some stream or 
lake and are then turned upside down on a fence-post to 
dry in the air. By this practice the pails are withdrawn 
from the" careful supervision which the farmer himself or 
his superintendent may give to them when kept at the 
farm, and the pails are not thoroughly scoured and cleaned 
during the whole summer. In corners of milk-pails cleaned 
in the manner given and kept in the pasture I have found 
a slimy creamlike substance resembling coagulated milk. 
When the substance was shown to the dairymaid she was 
greatly surprised and could not understand how so much 
milk could remain in the pail. By closer inspection this 
whole whitish mass proved to be nothing but molds and 
bacteria. They had presumably daily fed on insignificant 
milk-remnants and strongly multiplied in the summer heat. 

* On dairy farms in northern Europe, during the summer months, 
the cows are usually milked in the pasture or in an enclosure of the 
same. — W. 



70 MODERN DAIRY I'RACTICf:. 

At other farms the milk-pails are kept in the cow 
stable. The inadvisability of this method ought to be 
easily seen by everybody. The air in the stable is seldom 
so pure that the pails will not be highly infected there. 
Their cleaning will furthermore always be more or less 
deficient under these conditions. It is not sufficient that 
the milk-pails are rinsed and scrubbed each time they 
have been used ; they must first be rinsed in cold water 
and then scrubbed with a brush and boiling hot water. 
By cleaning first with cold water, the milk remaining is 
removed from the corners and joints; if water above 70° C. 
is first used, some of the albuminoids of the milk are 
coagulated and will remain in the corners, from where they 
later can be removed with difficulty; such coagulated 
albuminoid substances are of course splendid nutritive 
substrata for the bacteria. 

The Use of Soda in Cleaning Milk-vessels. — In many 
places it is the custom to use boiling water to which 
soda has been added, for cleaning the milk-pails. The 
use of such a caustic is, however, not to be recommended; 
it only neutralizes or hides the acid that may be there, for 
that particular time, but does not expel the causes of the 
appearance of this acid. Einsing with water containing 
soda may, on the contrary, have injurious effects, as even 
after last treatment with ordinary water some lye may 
remain in the corners of the pails and make these remains 
a still better nutritive medium than the moisture remain- 
ing after rinsing with ordinary water. Soda should there- 
fore not be used indiscriminately for cleaning dairy uten- 
sils, but only in case of vessels in which sour whey, etc., 
has been kept. In using water containing soda the last 



SOURCES OF INFECTION IN THE STABLE. 71 

traces of the soda must be removed by repeated rinsings 
with common water. 

It is a very good plan to dip the milk-pail in boiling-hot 
water at the end of each cleaning. This will make the pails 
dry almost instantaneously, even in the joints, and a large 
number of bacteria but little tenacious of life (like, e.g., 
the one causing the milk and butter disease at Duelund 
mentioned before, see p. 20) will be destroyed. It is also 
advisable to steam the pails once a week, especially in 
winter. 

The milk-cans used for hauling ought to be treated in 
the same manner after each use, with the difference that 
steaming ought to be obligatory in their cleaning. Steam- 
ing is the strongest weapon against bacterial growth in the 
cans and should be applied far more than is now the case. 
By the word cleanliness we do not undei'stand the same 
now as in former days. In it is included all that heretofore 
was included under the term and a new point has been 
added — freedom from bacteria: cleanliness now also in- 
cludes sterility. Absolute sterility can of course never be 
reached in a business like practical dairying, but it is 
nevertheless the duty of every dairyman to try to reach a 
certain degree of sterility in the milk cans and pails which 
may be easily obtained in any modern creamery by means 
of steaming. 

Steaming Milk-vessels. — A good method of arranging 
the steaming is, e.g., to conduct one or two steam-pipes 
under the floor or under a low table near the sink by an 
arrangement like that shown in the accompanying illustra- 
tion (Fig. 22). 

When the milk-can has been scrubbed clean, it is 
turned upside down over the steam-pipe and steam is 



72 



MODERN DAIEY PRACTICE. 



turned on. In this way all cans may be easily and rapidly 
steamed and practically sterilized. If absolute sterilization 
is wanted, it can be obtained more easily by repeating the 
steaming a couple of times with short intervals than by 
one uninterrupted long steaming. When the milk-cans 
have been steamed, they are left upside down, unless cov- 




FiG. 22.— Arkangement for Steaming Milk-cans. 

ered by a lid, until they are to be filled again. This is 
to prevent the introduction of bacteria into the cans, the 
bacteria being, as before mentioned, subject to the law of 
gravitation. 

The steaming of the milk-cans can usually take place 
only at creameries, as the proper facilities are lacking on 



SOURCES OF INFECTIOK IN THE STABLE. 73 

the farms. If the steaming is done by means of a number 
of pipes according to the plan shown in the illustration, 
the operation spoken of will not take long. 

As the patrons of a creamery take back their skimmed 
milk immediately after the separation it is not usually 
practical to steam the cans in the creamery. In that way 
one of the most effective means of securing good milk is 
not taken advantage of, however. To get his milk-cans 
steamed every patron should bring some extra cans along, 
and they may then in turn be left in the creamery to be 
thoroughly cleaned and steamed. 

This does not imply, however, that the cans are not 
also to be cleaned at the farm as well as the conditions 
will permit. The Swedish writer K. F. Lundin gives in 
his book, " The Main Conditions for Furnishing Good 
Milk to the Creameries," a sad but true picture of how 
bad matters generally stand in this respect. Although 
intended for Swedish conditions, his description may 
equally well be applied to our country. He says among 
other things: 

" Almost daily the author while on duty has had occa- 
sion to notice how milk-cans are left at railway depots, at 
roadsides and crossroads, with closed covers, often in the 
full heat of the sun the whole day until evening, although 
the farms often do not lie more than a stone's throw from 
the place, and the cans might easily be brought over and 
cleaned. Such a practice cannot be called anything but 
unpardonable carelessness and gross negligence. The re- 
sults are soon felt. It is almost impossible, even by the 
most careful cleaning, to remove the foul smell which 
arises in the cans when thus kept covered in the heat of the 
sun. The milk remaining in the can from the creamery 



74 MODERIf DAIRY PRACTICE. 

has soured and dried solid on account of the heat, for 
which reason the cleaning is made greatly more difficult 
and perhaps not with the best of intentions thoroughly 
effected in the hurry, since people often do not remember 
to clean the cans till the very moment when again they 
are to be used. There is no time to more than just rinse 
the can and rush around its inside with an old dish-rag 
which is sometimes dirtier than the can itself, having 
often before been used for the same purpose. This is 
not exaggerated, but is often met with in practice, I am 
sorry to say. The farmer himself may be ignorant of the 
manner in which the cans are taken care of, but he has 
careless servants and does not exercise sufficient super- 
vision over them. When the milk is poured into such 
vessels one cannot be surprised if it is damaged and comes 
to the creamery in a diseased condition. 

" At many creameries we have also had occasion to see 
that there are patrons whose milk is sour and bad-flavored 
on its arrival at the creamery. It ought not to be harder for 
these than for the rest to keep the milk sweet. The whole 
fault lies in the lack of cleanliness. Therefore the best way 
to remedy the evil is mercilessly to send back such milk. 

" If the milk-cans are examined more closely and the 
hand brought around in them, we shall in some cases find 
a greasy, yellowish and putrid substance, an evident proof 
of the manner in which the cans are kept clean/' 

Annual Cleaning of Stable. — Besides the careful clean- 
ing explained in the preceding, which must take place 
daily on the farm, a thorough cleaning combined with dis- 
infection should be made at least once a year. In this 
process the whole stable must first be emptied and all 
remnants of fodders, manure, litter, etc., be carried away. 



SOURCES 0^ INFECTION IN THE STABLE. V5 

The whole stable is then to be scraped clean and swept, 
all hooks and corners, all joints in walls and JBoor; the 
ceiling is freed from dust and cobwebs by means of a stijff 
broom. The sweepings are at once to be removed from 
the vicinity of the stable and either burned (this is essen- 
tial if any contagious disease has appeared in the herd 
during the year) or else ploughed under in the field. They 
ought never to be left uncovered near the stable, e.g., on 
the compost heap outside the same, for in this case the 
same filthiness filled with bacterial life may again enter 
the stable or else be introduced to the living-houses, etc. 

The ceiling, floor, and walls in the stable having been 
scraped clean, both they and the tools ought to be care- 
fully scoured and finally rinsed with boiling-hot water; 
small pools of water possibly remaining in recesses must 
be well wiped up. 

If a mow for keeping coarse fodders, etc., is found in the 
stable it should also be emptied and cleaned every spring. 

Whitewashing the Stable. — If no contagious diseases 
have appeared among the cattle in the stable since the last 
general cleaning, disinfection of the stable is not abso- 
lutely necessary. After the cleaning, the inside of the 
stable should be at once whitewashed. To prepare milk of 
lime 100 parts (by weight) of quick-lime are mixed with 60 
parts of water, and a quart of the powder-like slaked lime 
is then mixed with 5 quarts of water. The milk of lime 
is well stirred before being applied. Walls and ceilings, 
pillars, etc., are brushed with lime-water, an effort being 
made to have it soak into cracks and corners as much as 
possible. By this whitewash, which is very cheap, sev- 
eral advantages are gained : the stable becomes lighter and 
more cheerful, the woodwork is preserved, and, what is 



t6 MODERN DAIRY PRACTICE. 

still more important, the development of micro-organisms 
is checked for some time, as the lime-water acts as a weak 
antiseptic. To become very effective the whitewash ought, 
however, to be repeated during the summer. 

Disinfection of Stable. — In case contagious diseases 
have appeared in the stable since the last thorough clean- 
ing took place, or if the milk in spite of all precautions 
has still proved strongly infected in the stable, the liming 
ought to be preceded by a disinfection of the stable. This 
may be effected in various ways. I shall here describe a 
method in use at an estate in Germany which is reported 
to have given good results. 

After having scrubbed, cleaned and aired the stable, 
as directed, all doors, wickets, windows, flues, etc., are 
shut. If straw or hay is found in the mow it must be 
removed. The less leaky the doors, etc., are the better. 
Several earthenware plates with chloride of lime are now 
placed in the stable and crude muriatic acid poured over 
them. Chlorin gas is then generated, which will kill the 
bacteria. It must be remembered that this gas is injurious 
also to man, especially for the respiratory organs, for which 
reason one must leave the stable as quickly as possible 
after the addition of the acid; the stable is now kept shut 
up for twenty-four hours and then thoroughly aired. If 
the stable is well closed an application of one pound of 
cMoride of lime and three pounds of crude acid may suffice 
for every 5000 cubic feet. After airing, all woodwork, as 
window-sills, mangers, beams, etc., are carefully scrubbed 
and washed with boiling-hot water. 

Sulphurous acid, which is generated by burning sulphur 
in a suitable dish, has also been used for disinfection of 
stables; it acts only in the presence of moisture. Recent 



SOURCES OF INFECTION IN THE STABLE. 77 

investigations have shown, however, that the disinfecting 
power of this agent is small even if it is allowed to act for 
a long time. 

It is to he remembered that disinfection with chlorin 
is generally more effective than an application of any dis- 
infecting fluid, since the gas will be able to penetrate into 
all the small cracks and crevices. 

The disinfection described is best made in the spring, 
soon after the cows are let out on pasture. The wood- 
work will then soon dry, and the whole summer may be 
taken for the perfect airing of the stable — an operation 
which must not be neglected even if no disinfection is 
made. If the stable is provided with a wooden floor, some 
floor-planks should be taken up, so as to facilitate the 
drying and cleaning of the space under the floor. The 
stable-loft must also be aired in summer-time. 

Another good way to fight the bacterial growth gener- 
ally so luxuriant in stables is to wash all woodwork with 
warm coal-tar in the spring after the cleaning and airing. 
If the floor in the stable is made of bowlders (which in 
general must be considered unsuitable, however), all filthi- 
ness between the stones must be carefully removed, the 
interstices thoroughly soaked with a solution of chloride 
of lime (one pound to six quarts of water), and the floor 
leveled with new sand. If the stable is supplied with 
earthen floor (which, also, for many reasons cannot be rec- 
ommended), five to six inches of the upper layer ought to 
be carted off, the underlying dirt wet with the chloride-of- 
lime solution mentioned, and new dirt filled in. 

If this disinfection is made during the spring, all kinds 
of carbolic-acid preparations may be used instead of the 
chloride of lime; but disinfection with carbolic acid must 



78 MODEKN DAIRY PRACTICE. 

not be made later during the summer, since it will take a 
long time before the strong carbolic-acid smell is gone, 
and as the milk very quickly will take up all kinds of 
odors and be tainted by it. A suitable carbolic-acid solu- 
tion may be obtained by dissolving soda in water and milk 
of lime, adding some crude carbolic acid to the solution. 
This mixture has proved effective in disinfections after all 
kinds of epidemic diseases. 

In my opinion the safest method is to disinfect the 
stable, even when infectious diseases have not appeared 
there. This method will doubtless tend to increase the 
keeping quality of the milk and its products. In this con- 
nection I will mention that the milk epidemic at the 
Duelund estate in Denmark (see page 20) did not dis- 
appear until after a thorough disinfection of both stable 
and dairy. 

In the January number of the Annales de VInstitut 
Pasteur, 1891, appearing after the above chapter was 
written, Prof. Duclaux gives a full account of some experi- 
ments which confirm the main principles for the treatment 
of milk laid down in the preceding pages. 

" It seems to me," Duclaux says,* " that instead of 
going farther in this direction [sterilization of the milk by 
heat], it would be well to turn around and ask if it were 
not better to avoid that the heating become necessary, i.e., 
prevent all injurious bacteria from entering into the milk. 
In an address which I made during the World's Fair, on 
June 7, in Trocadero Hall, I said that milk from a well- 
kept cow stable, milked very rapidly into a carefully- 
cleaned pail, by a milker who washed well his hands and 
the teats of the cow, does not sour more rapidly than 

* Loc. cit., vol. 5, p. 59, 



SOURCES OF INFECTION IN THE STABLE. 79 

milk drawn without care and to which soda was added 
in order to hide its lack of cleanliness. This thought 
arose in me through the strong power of resistance 
which I have noticed in milk which was milked with 
extra precautions in my presence. It was taken up by 
one of my hearers — Dr. Smester* — who applied it in 
Normandy. He is now sending milk to Paris which 
luis not been heated or received any chemical preserv- 
atives, but which still keeps for a long time, even in hot 
weather. It seems to me that we ought to improve in 
this direction, — at least when the question is of milk in- 
tended for rapid consumption, — and that we ought not to 
try to multiply and further perfect the pasteurization 
apparatus. It is true that an improvement of these will 
bring about a perfect neatness on the farms and among the 
farmers, and that an industrial tool is created sooner than 
traditional habits are changed. But a change would soon 
occur among the producers, if only the consumers demand 
the same. When the latter really want clean milk they 
will get it. As matters now stand it is always safest to 
boil the milk before using, if the consumer is not fully 
certain of the cleanliness and general health of the animals 
producing it; but the question of the keeping quality of 
the milk will nevertheless have taken a great step toward 
its solution when it is correctly understood on farms and 
in dairies what cleanliness really means." 

* Dr. Smester is contiauiug his experiments with a view of 
applying them on a large scale. 



CHAPTEK III. 

THE COMMON FORMS OF BACTERIA FOUND IN 
COWS' MILK. 

The milk when drawn from a healthy udder being 
sterile (see p. 23), the kinds of micro-organisms found in 
the same are dependent on the forms of bacteria found in 
its surroundings. For this reason we generally find differ- 
ent kinds of bacteria in different places, and can often form 
an opinion concerning the company it has kept from a 
mere microscopic examination of the milk. I shall here 
only recall a couple of instances described in the preceding. 
The presence of lacilhis suMilis in the milk shows plainly 
that in some way or other it has been exposed to fodder 
dust, etc., while the presence of peptonizing, putrefactive 
bacteria in large numbers indicates that the milk has been 
in too intimate contact with manure particles and other 
filthiness. Still more certain pointers as regards the causes 
of the infection of the milk, are obtained by microscopic 
examinations of the non-bacterial impurities, as described 
in the preceding chapter (see p. 31). 

Different forms of bacteria are usually found in the 
milk during the different seasons, for the reason that the 
surroundings of the milk during its production and hand- 
ling are not the same during different periods of the year. 
As is natural, the greatest differences are found between 
samples of milk taken when the cows were kept in the 

80 



BACTERIA COMMONLY FOUND IN COWS' MILK. 8i 

barn and when they were on pasture. According to my 
observations, these two kinds of milk differ from one an- 
other not only in the fact that the milk produced while on 
pasture contains a much smaller number of bacteria, but 
also because the organisms found in it are by no means as 
dangerous for the keeping quality of the milk as those in- 
fecting the milk originating in the stable. This is espe- 
cially striking if the pasture milk is compared with milk 
from a dark and dirty cow-stable where the cows are stand- 
ing on manure. 

In view of the conditions mentioned, we cannot here 
enumerate all or even the most common micro-organisms 
found in the milk.* We shall only consider the varieties 
which, according to my investigations, are the most dan- 
gerous enemies to the keeping qualities of our milk. There 
may, of course, be a large number of other bacteria which 
in certain regions, where I have not had an opportunity to 
examine the milk, play a still more injurious part than 
those here mentioned. 

My investigational material has come mainly from 
middle Savolak, or from the regions around Helsingfors 
and Tammerfors. A large number of samples examined, 

* For a detailed enumeration of the different forms of bacteria 
found in cows' milk, see Kramer, " Bakteriologie d. Landwirtscbaft," 
1893 ; Freudenreich, " Bakteriologie der Milchwirtschaft," 1893, pp. 
36-53; Conn, "The Fermentations of Milk," 1893, pp. 17-63 ; Ada- 
metz, "Normal and Abnormal Bacteria in Milk," Oest. Monatschr.f. 
ThierJieilkunde, 15, pp. 1-36 ; Centralhl.f. Bad., 8, 109 ; Schuppan, 
" Bacterien in Bezieh. z. Milchwirtschaft," Centralbl. f. Bad., 13, 
527; LoflBer, "Ueber Bacterien in d. MUch.," Berl. klin. Wochen- 
schr. 1887 ; Hueppe, " Untersuch. ueber die Zersetzimgen d. Milch 
durch Mikro-organismen," Mitt. Kais. Ges. Amies, 2, 309. — W. 



83 



MODERN DAIRY PRACTICE. 



especially of sour milk, buttermilk, and sour cream, came 
from different regions of our countrjo 
Samples of sweet milk have generally been 
examined at once after they came into my 
possession. 

Other samples, taken on travels in the 
different districts, were usually not examined 
at once, no facilities being available. These 
samples were kept in thin, short, previously 
sterilized glass tubes, drawn out to fine 
points in both ends, and at once melted to- 
gether. The illustration (Fig. 23) shows 
such a tube in natural size. In using it 
the outer wall of the tube which is introduced 
in the milk is sterilized over an alcohol flame, 
the points are broken off rapidly with a pair 
of recently ignited nippers, the milk is sucked 
in, and the ends again melted together. A 
careful record was kept of the outward ap- 
pearance, color, taste, and odor of each sample 
of milk, and of conditions in the dairy and 
barn on the farms where the milk was pro- 
duced. In cases where samples of tuberculous 
and other contagious or abnormal milk were 
taken I used a sterilized glass tube of a some- 
what different shape than the one just de- 
scribed, since it was undesirable in such 
cases to get any of the milk into the mouth 
in filling it. The latter kind of sampling 
tubes are of about double length, and supplied 
Figs. S3, 24. with two reservoirs for the milk, of which the 

one only served as a safety bulb in sampling (Fig. 24). 



BACTERIA COMMONLY FOUND IN COWS' MILK. 83 

The examination of the samples taken and kept in 
this way cannot of course give any information of the 
number of bacteria in the original fluid, as quantitative 
bacteriological analyses, as shown in the Introduction, must 
be made immediately after the sampling. Tl>e method 
used will, however, throw a clear light on the question 
of the varieties of bacteria found in the different samples. 
It is possible that some kinds of bacteria may become less 
active, or even succumb, if the sample is kept too long; 
but all control analyses which I have made have failed to 
show any appreciable decrease in the number of the living 
kinds of bacteria, even after a lapse of three months. A 
long confinement in the glass tube appears, on the other 
hand, to cause the destruction of some forms of bacteria, 
while lactic-acid bacteria have shown strong ability to 
multiply even after having been kept for fourteen months 
in the manner described; their ability to develop lactic- 
acid fermentation in milk was, however, considerably 
weakened. 

Number of Bacteria in Milk. — The number of bacteria 
in cows' milk depends of course on the treatment to 
which the milk has been subjected since drawn from 
the udder. This explains the different data given in the 
literature on the subject. Cnopf in Munich counted the 
number of bacteria in recently drawn milk. He found no 
less than 60,000 to 100,000 bacteria in one cubic centimeter. 
Freudenreich in Eiitti, Switzerland, on the other hand, 
found only 9300 per cc. in milk on its arrival in the labora- 
tory. Jensen in Copenhagen says he is inclined to think 
that the number of bacteria in the milk cans immediately 
after all the cows have been milked is many times larger 
under ordinary Danish conditions than given by Cnopf. 



84 MODERN DAIRY PRACTICE. 

The results found by me in case of different samples of 
milk have also varied greatly, according to the age of the 
sample when the bacterial content is determined, as well as 
the origin of the milk analyzed. 

Samples taken in a pasture on a fresh, somewhat damp 
summer morning showed the following average results as 
regards their bacterial content : 

Immediately ^ , „ , 

after Milking. ^ '^^^^- ^ *^°'^'^^- 

Number of bacteria in ) t^ oo ikoa 

one cubic centimeter, \ 



The numbers in this table are surprisingly small as com- 
pared with those previously given, but the samples were 
taken under particularly favorable conditions. The milk- 
ing took place away from any dwelling-house, in a pasture 
surrounded by woods, during comjDlete calm, and the cows 
were still damp after the moisture and the fog of the night 
air. The infection under these conditions would naturally 
be very small. During the two hours given in the table 
the milk stood in the hauling can in the pasture and during 
the transportation to the dairy. 

Entirely different data are obtained in examining millc 
produced in a tarn. The infection is there very pro- 
nounced, even within the first half-hour after the milking 
is done. 

In making some quantitative bacteriological analyses 
of the milk produced on a certain farm I obtained samples 
of milk from a stable where only the heavy milkers had yet 
been taken in from the summer pasture. The stable was 
therefore not filled with cows, and ordinary winter condi- 
tions had not yet appeared there. This explains why this 
milk also contained comparatively few bacteria. 



BACTEEIA COMMONLY FOUKD IK COWS' MILK. 85 

J,rMiiSf. *tour. lihou,,. 

Number of bacteria per ) ^^a nan o^kk 

cubic centimeter \ ^^^ ^^^ ^^^^ 

The milk was kept in the hauling-can in the stable dur- 
ing the 1^ hours after the milking. The mouth of the 
can was covered by a clean, thin linen cloth thrown loosely 
over it, which did not exclude the air, but to a large extent 
prevented possible new infection from bacteria in the air.* 

It was found in these experiments that immediately 
after the milking a very varying number of bacteria was 
found in the different layers of the milk. I was of the 
oj)iuion that since the milk in the pail is under constant 

* Sedgwick and Batchelder {Boston Med. and Surg. Journal, Jan. 
14, 1893) in studying the Boston milk supply made the following 
experiments : "Milk was drawn from a clean and well-kept Hol- 
stein cow in an unusually decent stable. The normal milk of this 
cow had already been repeatedly proved to be sterile. Milk drawn 
by hand from this cow with great care into sterilized bottles, and 
planted quickly, yielded as an average of several trials 530 bacteria 
per cubic centimeter. When, however, the milkman used the ordi- 
nary milk-pail of flaring form, seated himself with more or less dis- 
turbance of the bedding, and vigorously shook the udder over the 
pail during the usual process of milking, we found that the numbers 
were very much higher, namely, an average of 30,500 per cubic 
centimeter at the end of the milking. When such milk is found 
upon the tables of country families a few hours later it naturally 
shows still more bacteria, doubtless because those with which it was 
seeded have had time to multiply, The average of fifteen such sam- 
ples frorn the tables of families in Jamaica Plain, Cambridge, and 
Auburndale was 69,143 per cubic centimeter. In these cases, 
moreover, the conditions of the cows and of the stables were excep- 
tionally good, while the milkmen were much more than ordinarily 
clean and careful." — W. 



86 MODERN DAIRY PRACTICE. 

stirring during the milking that the bacterial content 
would be about even in the whole of the can. But control 
experiments showed in a very striking manner that the 
member of bacteria ivas largest on the surface of the milk. 
All samples taken from the depth of the mess of milk, by 
means of sterilized, so-called Pasteur pipettes showed 
very few bacteria, — on an average 20.3 per cc, — while all 
samples taken from the surface contained over 200 per 
cc. If I should venture an explanation of this phenomenon, 
I would say that it still more confirms the observations 
made in the preceding, that one of the main sources of the 
infection of the milk is the lower part of the stomach and 
the udder region of the cow, from which filthiness with ac- 
companying bacteria all the time is falling down during 
the milking. 

Milk from stables where winter conditions have entered 
has usually shown a higher bacteria content. Bacteriologi- 
cal analyses of such milk half an hour after the close of 
the milking have given the following data for the content 
per cubic centimeter: 4100; 2450; 1890; 14,670; 830; 
3030; 5450; 21,700; and 1030. 

I have made bacteriological analyses of several sainples 
of milk sicpplied to creameries, the samples being taken 
under different conditions. The results naturally differed 
greatly. Milk from a well-conducted farm was examined 
after standing for one hour in the warm stable and then 
hauled to the creamery near by. The milk contained on 
an average 4500 bacteria per cubic centimeter. Milk 
from a filthy stable where the cows Avere standing in 
manure, on a warm day, transported by rail to the city 
where I took the sample, seven hours after the milking, con- 
tained 25,000 bacteria per cc. After having been kept 



BACTERIA COMMONLY FOUND IN COWS' MILK. 87 

for an hour in the rather warm laboratory the sample was 
found to contain considerably over 100,000 organisms per 
cubic centimeter. From a filthy and dark cow stable, 
spoken of more in detail in Chapter V, a sample of milk 
came which three-fourths of an hour after milking showed 
not less than about 670,000 bacteria per cc. The bac- 
terial content of three samples of milk taken on three 
consecutive days from this stable, did not vary much, 
the analyses showing the following average figures per 
cc. : 730,000, 560,000, and 780,000. The most infected milk 
ever analyzed by me was from a milk store in Wiesbaden 
(Germany). Its age and the treatment to which it had 
been subjected could not be ascertained. It was sold as 
fresh new milk, did not taste sour, but had a decided " off " 
flavor; on analysis it was found to contain an immense 
number of bacteria, according to a low estimate several 
tens of millions per cubic centimeter. Any exact figures 
in this analysis could not be obtained by the methods then 
at my disposal.* 

* The influence of the season on the bacterial content of milli is 
illustrated by the data furnished by Dr. Russell as given on p. 93, 
foot-note. 

The weather doubtless also greatly influences the number of bac- 
teria found in milk. Dr. Russell has kindly furnished me with the 
following illustration • The milk of one of the patrons at the Wis- 
consin University Creamery was examined in May 1894, on two 
succeeding days, the sampling being done .it the same time both days; 
it contained 1,150,000 and 48,000 bacteria per cubic centimeter, on 
an average, during the two days. The flrst day was very warm, 
while the second was cold and rainy. 

The milk contained seven to ten different species of bacteria; slimy 
organisms were isolated in large numbers ; hay bacillus was quite 
numerous, and pitted liquefiers very numerous in the sample. — W. 



88 MODERN DAIRY PKACTICE. 

Increase in Bacterial Content of Milk. — The increase 
of the bacteria in milk depends of course both on the tem- 
perature and on the kinds appearing in the milk. The 
influence of the former factor is shown by the following 
investigations : 

Cnopf and Escherich in Munich found 60,000-100,000 
bacteria per cc. in a sample of milk recently drawn under 
precautions of great cleanliness. This milk was kept in a 
cool cellar at a temperature of 12°.5 C. (56°.5 F.). After 
two hours the number of bacteria was 4 times larger than 
at the beginning, after four hours 8 times larger, after five 
hours 26 times larger, and after six hours 435 times larger. 
[Another portion of the same milk was kept at 35° C. in 
an incubator; the bacteria contained in it had multiplied 
23 times after two hours and 215 times after four hours, 
1830 times after five hours and 3800 times after six hours. 
The development of bacteria in milk kept on ice was so 
small during this time that it could hardly be ascertained, 
but in the course of some days it reached as high figures as 
in the other samples.* — W.] 

From the laboratory at Riitti the following table is fur- 
nished concerning the number of bacteria per cc. in 
milk of Nov. 14, 1889. On the arrival at the laboratory 
there was found 9300 bacteria per cc. in the milk. 

Incbease in Bactebial Content. 

When kept at When kept 

25° C. at 35° C. 

2 times 4 times 

18.5 « 1,290 " 

107.5 " 3,794 " 

62,097. '' 5,376 " 
* Oentralb. f. Bakteriologie, 6, 554. 





When kept at 
15° C. 


3 hours later 


1.06 times 


6 hours later 


. 2.5 " 


9 hours later 


. 5.0 « 


24 hours later . . , 


,. 163 " 



BACTERIA COMMONLY POUND IN COVVS' MILK. 89 

The following instructive facts are shown from these 
figures:* 1. At 15° 0. (59° F.) there was no increase dur- 
ing the first three hours, and during the first six hours only 
an insignificant one. 2. At 25° C. (77° F.) the increase was 
insignificant during the first three hours, but the number 
of bacteria then increased rapidly at the temperature 
so favorable to the growth of the bacteria. 3. At 35° 0. 
(95° F.) the development was rather rapid from the start, 
but the increase in the bacterial content was still after 
twenty-four hours not so large as at the last-mentioned 
lower and evidently more favorable temperature. 

If a still lower temperature than 59° F. (15° C.) be used 
for keeping the milk the bacterial growth is nearly com- 
pletely checked. If the temperature of the milk is low- 
ered to 45° F. (7° C.) immediately after the milking, the 
bacterial content according to my results is practically 
unchanged after twenty-four hours, and even after a still 
longer time from what it was at the beginning of the cooling. 
I have, however, observed in isolated cases that even at this 
temperature a considerable increase has taken place; this 
increase always stopped entirely when the bacteria were 
subjected to this temperature for 5-6 hours. The bacteria 
able to multiply even at 45° F. (7° C.) thus appear to be 
slowly paralyzed under the influence of this temperature. 
Even when the milk has had a temperature of 43° F. 
(6° C), an increase of the bacteria has twice been found: 
in the one instance the increase, strange to say, took 
place a long time after the temperature of the milk had 
been lowered to this point. The tenacious organisms 

* See also results obtained by Miquel, A?in. Microgr. 1889, Dec. 
No. ; and by Baumanu (Inaug. Dissert. Univ. Konigsberg, 1893, pp. 
16,17).— W. 



90 MODEKN DAIRY PRACTICE. 

which thrived so well at this low temperature were not, 
however, of a kind that would exert any influence on the 
quality of the milk. With the temperature of the milk at 
39° F. (4° C.) I have never, no matter how long it was 
kept, been able to observe any increase in the bacteria con- 
tent; this has always remained unchanged from the mo- 
ment the temperature sank to 39° F. (4° C). 

It may finally be mentioned that Cnopf * analyzed milk 
samples which contained from 200,000 to 6,000,000 bac- 
teria per cubic centimeter 5-6 hours after the milking 
(average over 1,000,000 per cc.).t 

* Centralbl. f. Bad. 6, 553. 

f The determinatious of the bacterial content of market milk or 
of milk peddled in cities have as a rule given exceedingly high fig- 
ures, owing to the comparatively long interval between the milking 
and the sampling. The following results have been obtained in the 
main investigations in this line : 

Clauss (Inaug. Dissert. Wilrzberg, 1890 ; Chem. Centralbl. 1890, 
518) found from 232,000 to 2.3 million bacteria per cubic centimeter 
in eight samples of WUrzburg market milk taken during winter 
time ; average 1-2 million per cc. 

Hohenkamp {Arcli. f. Ilyg., 14, 260) found from 1.9 to 7.3 mil- 
lions in the market milk of the same city during the summer. 

Buiwid {vide Knochenstiern) in 1890 found on an average 4 mil- 
lion germs in sixteen samples of Warsaw milk. 

Freudenreich (mt^e Knochenstiern) found 10,000 to 20,000 bacteria 
per cc. of Rlitti milk. 

Geuns {Arch. f. Hyg., 3, 479) found fresh milk sold in Amsterdam 
to contain 2.5 millions, and when ten hours old 10.5 millions. 

Cunningham {Arch. f. Hyg., 12) found 3400 to 300,000 bacteria 
per cc. of Calcutta milk taken during summer 1891. 

Renk {Centralbl. f. Bad , 10, 193) found 6-30.7 million per cc. in 
Halle milk. 

Uhl {Zeitschr. f. Hyg., 12, 475) found from 88,100 to 170 millions 
av. 22.9 millions, in thirty samples of Giessen market milk, taken 



BACTERIA COMMONLY FOUND IN COWS' MILK. 91 

Comparing the data just given concerning the number 
of bacteria found in milk, it will be seen that milk under 
certain conditions may contain very few bacteria and 
under other conditions immense numbers of these organ- 
isms. That the latter is always the case with milk com- 
ing from filthy stables is apparent from the data given, 
and it is equally apparent that cleanliness and neatness in 
the handling of the milk may cause a considerable decrease 
in its bacterial content.* 

during May 1892, and from 10,500 to 13.6 millions, av. 2.9 millions, 
in the same kind of milk sampled during June 1892. 

Knochenstiern (Inaug. Dissert. Univ. Dorpat, 1893) obtained tlie 
following results in his investigations of the Dorpat milk supply : 
40 samples of milk sold by milkmen : 

36,000-83 millions; av. 10.2 millions 
25 samples of milk from village dairies : 

90,000-103 " " 13 
35 samples of milk sold on market-place : 

137,000-287 •* " 25 •' 
40 samples of milk sold in milk stores : 

11,600-257 " "30 

Gernhardt (Inaug. Dissert. Univ. Jurjew, 1893) found similar re- 
sults for Dorpat milk. 

See also Baumann (Inaug. Dissert. Univ. Konigsberg, 1893, pp. 
16, 17).— W. 

* The number of bacteria in American milk has been studied by 
but few investigators. Sedgwick and Batchelder examined the milk 
supply of Boston bacteriologically {Boston Med. and Surg. Jour., 
1892, Jan. 14) ; the average number of bacteria found in fifty-seven 
samples in the spring of 1890 was 2,355,500 per cubic centimeter. 
Sixteen samples obtained from groceries contained 4,577,000 per cc. 
Ten samples collected from "well-to-do families upon the Back 
Bay " showed an average of 1,438,000 per cc. The lowest number 
found in Boston milk supplied in the ordinary way was 30,600 per cc. 

Dr. Russell (private communication) determined the bacteria con- 
tent of morning milk as delivered to customers in Madison, Wis. : 



92 MODERN I»AIRY PRACTICE. 

Kinds, not Numbers, of Bacteria of Most Importance. 

— It must be remembered, however, that in the infection 
of milk with bacteria, as in every other infection, the main 
importance does not lie in the large or small number of 
bacteria, but in their qualities and nature. It is a com- 
mon observation that a large number of different kinds of 
bacteria are found in the milk by the first examination in 
the stable, but in later examinations of the same milk 
the number of different kinds will be found considerably 
reduced. The struggle for existence thus seems to be as 
pronounced in the microscopic as in the macroscopic 
world. The milk is infected from different sources by 
different kinds of bacteria, and each of them begins to 
hunt for sustenance in the new nutritive medium, and 
seeks to gain superiority over the others. The struggle is 
for life and for the greatest power, for even among these 
pygmies of the living world the old maxim holds good, 
that he who has the power appropriates for himself all the 
good things of life. The organisms, for one reason or 
another gaining the upper hand, increase so rapidly that the 
others at best can only just save their lives, and are unable 
to exert their vital functions on a large scale. They remain 
helplessly in the minority as long as the conditions are favor- 
able for their more favored conquerors. We thus find that 
only a few forms of bacteria have been able to increase in 
preponderating numbers in samples of milk that have been 

from 35,000 to 275,000 was found per cc. on an average during April 
(1894), aud from 380,000 to 2,000,000 per cc. during May and June 
See also foot-note on p. 87. 

Pammel {Iowa Experiment Station Bulletin No. 21, p. 801) found 
571,900 bacteria in milk " just before the curd was ready to cut for 
cheese" ; another sample contained 165,000 bacteria per cc. — W. 



BACTERIA COMMONLY FOUND IN COWs' MILK. 93 

kept for about one day. Among the determining causes 
for the superiority of these few forms three circumstances 
may especially be pointed out : 

1. The milk is a better nutritive medium for these 
organisms than for their competitors. Although milk in 
general may be considered an excellent growing place for 
bacteria, certain kinds seem to be especially adapted to 
development in this substratum. 

2. The temperature present is more favorable for the 
conquering kinds than for the others. Experience shows 
that a difference in temperature of 2°-4° F. may have a 
decided influence on the development of bacteria, a fact 
which is apparent in a striking manner in the manufac- 
ture of the different kinds of cheese. 

3. If the milk has become largely infected with a cer- 
tain kind of bacteria, this is very apt to keep the superior- 
ity, even if the milk generally speaking is not a very 
good nutritive medium for it. Such " mass-infections " 
of a certain bacteria frequently occur in the handling of 
the milk on the farm. Accidents seem to play an impor- 
tant part in this matter. In several cow stables it seems 
to be the rule that such mass-infection takes place. This 
was, e.g., the case in a stable where, as mentioned in the 
preceding chapter (see p. 53), unclean straw and rusty 
chaff were used day after day. 

Fortunately, however, it is always not the case that the 
conquering species are injurious to the quality of the milk. 
I have seen examples where milk which was normal both to 
taste and smell, as well as to consistency in general, con- 
tained an immense number of bacteria which did not then 
interfere with the quality of the milk. Among the species 
found in such milk I have observed bacteria, which later on 



94 MODERN DAIRY PRACTICE. 

exerted a more or less injurious influence on the butter 
or the cheese made from the milk. 

Some bacteria may furthermore appear in the milk 
which do not in themselves have the power to change 
appreciably its quality, but which prepare favorable con- 
ditions for other, injurious bacteria. As a transition 
group between these organisms and those directly de- 
structive of the milk, some species may be included that 
are able both to change the quality of the milk to a 
considerable extent and to prepare a good field for other 
bacteria, which in their turn produce other kinds of fer- 
mentations. 

CLASSIFICATION OF BACTERIA FOUND IN MILK. 

In trying to classify the common forms of bacteria 
found in milk, I have separated them into the following 
four groups: 

I. Indifferent bacteria. 

II. Bacteria indifferent in milk, but active in the milk 
products. 

III. Indirectly injurious bacteria. 

IV. Injurious bacteria. 

I. Indifferent Bacteria. — The species belonging to this 
group are of course of small interest in studying the prob- 
lem of the bacteriology of the dairy, and will therefore not 
be described in detail here. In deciding certain questions, 
as, e.g., whether a certain sample of milk has been infected 
by bacteria in the air or by such originating in manure 
particles, the indifferent bacterial impurities may be of 
some importance. They seem, however, to show such a 



BACTEKIA COMMONLY FOUND IN COWS' MILK. 95 

different appearance in different localities that only after 
specific investigations of the local bacteriological conditions 
can there often be any question of applying them as decid- 
ing factors. 

II. Bacteria Indifferent in Milk but Active in its Prod- 
ucts. — The species belonging to the second group which I 
have met with will be described in later chapters. On 
account of the many difficulties met with in the examina- 
tion of these bacteria, I have unfortunately only to a small 
extent been able to throw any light on their nature and 
qualities. 

III. Indirectly Injurious Bacteria which Produce Fa- 
vorable Conditions for Bacteria Injurious to the Milk. — 
The third group includes first of all several bacteria caus- 
ing alkaline reaction in the milk. These bacteria may 
play also a certain part in the dairy industry of Finland. 
On a farm in Karelen, which I visited a couple of years 
ago, I found the housewife almost in despair. She said 
that tho milk had not soured properly during the whole 
summer, and as a result inferior butter was made during 
this time, while previously she had always prided herself 
on making a . mildly acid, first-class butter. Her supply 
of butter on hand also showed that she had every reason to 
be dissatisfied. The butter was mottled, insipid, and had a 
repugnant taste. During the early part of the summer the 
milk had soured, although it took a long time for it to 
do so; now the souring did not seem to be forthcoming 
at all. The milk stood in the pans for days, the cream 
rose, but did not thicken. It did not taste sour, and 
had no appreciable after-taste. Tested with litmus-paper 
the milk showed a distinct alkaline reaction. I was 
not able to investigate this interesting material bacterio- 



96 MODERN DAIRY PRACTICE. 

logically, as the samples taken in sterilized-glass tubes 
were accidentally lost. It may be added that since I could 
not arrange any disinfection of the dairy and milk vessels 
at the place, being far off in the wilderness, I had to advise 
her to seek a remedy entirely opposite to what I should 
have advised under different conditions — viz., to infect in 
every way possible the dairy, milk-pails, pans, churn, the 
cows' udders, etc., with sour milk from a neighboring farm, 
where the milk soured in the regular way. This " mass- 
infection" had the desired effect, according to what I 
learned on a journey in the same region during last sum- 
mer. 

A case of similar nature was observed during the same 
summer on an estate in Savolaks. It proved impossible to 
obtain ordinary sour milk at this place. The milk was 
left to sour in the usual way on the pantry-shelf, where it 
had always gone through the regular lactic fermentation 
during previous summers, and had formed good sour milk. 
Durinsr this whole summer the sour milk had been of a 
rather loose consistency and mostly of an insipid taste. 
When kept for some time it assumed an obnoxious, rotten 
taste. The milk soon showed smaller and smaller ten- 
dency to coagulate, while the bad taste appeared earlier. 
The cream rose rather rapidly to the surface and had a 
tough consistency (in this respect different from the ex- 
ample mentioned above), but the skim-milk was not viscous 
and had a characteristic greenish-blue color. The milk 
did not keep this appearance long, however. The surface 
of the cream turned grayish brown, and swelled in places 
on account of gas generation. At the same time a dis- 
agreeable smell and taste was noticed, for which reason 
the milk had to be removed from the larder. During 



BACTERIA COMMONLY FOUND IN COWS' MILK. 97 

several weeks it was impossible to prepare satisfactory 
sour milk on this farm, although the pans were finally 
placed in another room and the vessels were carefully 
cleaned. At last they began to inoculate the milk with 
ordinary sour buttermilk, and after a considerable time 
succeeded in this manner in making common sour milk. 
Not till late in the fall did the milk again turn sour in 
the ordinary way, without any separate inoculation being 
necessary. 

The greenish-blue skim-milk in the first unsuccessful 
sour milk gave a very distinct alkaline reaction and con- 
tained a large number of bacte.ia, among which a short, 
staff-like bacillus was especially noticeable. By pure cult- 
ures of this bacteria it was learned that it was in the main 
similar to the blue-milk bacillus {Bacillus cyanogenus) 
common in Germany, and more particularly similar to the 
form of it first investigated by Hueppe, and claimed by 
him to be the typical and regular cause of blue milk. This 
has been studied again of late by Scholl, and duly char- 
acterized as a variety (or species) distinctly different from 
the forms described by Loffler and others. It does not 
peptonize gelatine, but produces in the same a fine green 
coloring-matter resembling chlorophyll; the other kinds 
of bacteria produce a brownish coloration in gelatine. 
Neither the bacterium isolated by me nor the blue-milk 
bacteria found in Germany caused coagulation or fermen- 
tation of acid when inoculated in sterile milk; it was some- 
times observed that the milk was for a while viscous and 
thick-flowing. This, however, seemed soon to disappear. 
The milk turned alkaline if it previously was weakly acid 
or neutral. I have been unable to observe any blue colora- 
tion of the surface of the milk; the lower layers of the 



98 MODEKN DAIRY PRACTICE. 

milk seemed, however, to assume a greenish-blue colora- 
tion. 

Small micrococci appeared in the same milk, and these 
also produced a distinct alkaline reaction in it. The cult- 
ures in milk of this bacterium had a disagreeable odor, 
resembling that of ammonia. A mold, Oidium lactis, was 
also observed in large numbers in the milk. This is another 
micro-organism which produces alkaline reaction in the 
milk. The three latter organisms were by far the more 
numerous in the sample of milk mentioned. Lactic-acid 
bacteria were also found, but they had been largely sup- 
planted. In two calculations of the number of bacteria 
in one cubic centimeter the ratio of lactic-acid bacteria 
to bacteria producing the bluish-green color in the milk 
was about as 1 : 40,000. Unfortunately I was unable to 
obtain exact data as to this ratio by proper control ex- 
periments. The micrococcus mentioned was greatly in 
the minority, both in the cream and in the lower layers of 
the milk. 

By an analysis of this milk made since the change in 
the cream -layer spoken of had occurred, I was surprised to 
find the relation between the different species of bacteria 
greatly changed, as could readily be seen by the microscope. 
The micrococci had gained the upper hand in the cream 
layer, and the bacteria resembling the blue-milk bacillus 
had been forced to the lower layers of the milk, where they 
lived a very feeble life, as was proved by later examinations. 
Being aerobic bacteria, this might be inferred. The lactic- 
acid bacteria were in a very small minority during the 
whole experiment, both in the milk itself and in the cream 
layer. It is plain that the bacteria resembling the blue- 
milk bacillus produced favorable conditions for the micro- 



BACTEEIA COMMONLY FOUND IN COWS' MILK. 99 

cocci which can only multiply in a distinctly alkaline sub- 
stratum. When the milk once had this reaction due to 
the activity of the bacteria mentioned, they could develop, 
which they did to such an extent as to put their benefac- 
tors to flight. The cream then obtained the disagreeable 
taste and smell before mentioned as the last stage in the 
changes of the milk. 

According to my experience the moulds Oidium ladis 
spoken of, under which name several species seem to hide, 
often makes the substratum more favorable for vai'ious 
bacteria — a fact to which I have referred in an earlier pub- 
lication.* 

To the third group {indirectly injurious bacteria) some 
bacteria causing acidity in the milk may also be referred. 
They more properly belong to the fourth group, how- 
ever, and will be treated there. Although the bacteria 
in general require an alkaline or neutral reaction in 
the substratum, some are found demanding an acid reac- 
tion. These are, first of all, the butyric-acid bacteria. 
They thrive only in a strongly acid medium, and are there- 
fore most frequently found in sour milk, where they strug- 
gle for a living with the lactic-acid bacteria. These latter 
are thus their forerunners, which produce a favorable nutri- 
tive medium for the butyric-acid bacteria, and are then 
forced out of the way by these. Although the butyric-acid 
bacteria at first are only in an exceedingly small minority 
among the micro-organisms of the milk, they multiply rap- 
idly as soon as the substratum grows too acid for the 
lactic-acid bacteria, and begin to make their presence felt 

* " Saprofyta mikro-organismer i komjolk, I," Helsingfors, 
1890, p. 80; see also Lang and Freudemeich, "Oidium laciis in 
Milk ■' Ldw. Jahrb. Schw. 7, p. 221). 



100 MODERN DAIRY PRACTICE. 

by starting the bad-smelling lutyric fermentation ("ran- 
cidity"). These two processes — the lactic and butyric 
fermentation — seem to be coherent to such an extent that 
a German author (Wigand) recently even asserted that the 
butyric fermentation is simply a continuation of the lactic- 
acid fermentation (" ein weiteres Stadium der Milchsdure- 
gdhrung "). 

IV. Bacteria Injurious to the Milk. — Bacteria of very 
different kinds and of highly-varying characteristics belong 
to this group. In order more readily to obtain a general 
view of them, we will separate them into the following sub- 
divisions : 

1. Bacteria producing acidity in the milk. 

a. Bacteria producing lactic fermentation. 

b. Bacteria producing butyric fermentation. 

c. Bacteria producing volatile acids in the milk. 

2. Bacteria producing no acidity in the milk. 

a. Bacteria causing coagulation of the casein. 

b. Bacteria causing coagulation of the casein and 

subsequent peptonization of the coagulum. 

c. Bacteria bringing the casein into fermentation 

without coagulating it. 

We shall below briefly mention the main bacteria in- 
cluded under the preceding divisions. 

la. Lactic Ferment atio7i. — There are many kinds of 
bacteria producing lactic fermentation. Most of them 
belong to the bacteria proper, while others belong to the 
yeasts. The lactic-acid bacteria will be described more 
fully under the " Kipening of the Cream." 

Besides the lactic-acid bacteria proper, a number of 
other bacteria may be included under this division which 
only incidentally produce fermentation. Certain iufec- 



BACTERIA COMMOKLT ^OUND IN COWS' MILK. 101 

tious bacteria, as the Mastitis bacterium and some color- 
producing bacteria, as the Bacillus prodigiosus, belong here. 
The latter has not, to my knowledge, been found in our 
country.* 

Ih. Butyric Fermentation. — The form of the many 
butyric-acid bacteria which I have met with in this coun- 
try has in the main proved similar to the one first isolated 
and described by Hueppe. It is aerobic, and produces a 
slight coagulation of the casein, which, however, later on 
is peptonized. It may therefore also be referred to one of 
the following groups. If sterilized milk be inoculated 
with such butyric-acid bacilli, a clear liquid layer of a gray- 
ish color will be found after keeping the cultures for a 
couple of days at about 86° F. (30° C). Under this layer 
a lumpy casein coagulum is found, which sinks deeper 
as the clear liquid increases. The coagulum gradually 
disappears, and after some time will be entirely pepton- 
ized. Milk changed in this way has a very bitter taste. 

Ic. Bacteria Producing Volatile Acids. — Among the 
bacteria producing volatile acids in the milk may be men- 
tioned first the «c^mo-bacteria forms, which are rather fre- 
quent in milk. They all appear with a translucent, sack- 
formed cover, in which the fine, long, immovable bacteria 
are entirely wrapped up, and in which the division of the 
bacteria seems to take place. Some hours after the ster- 
ilized milk has been inoculated with such bacteria the sam- 
ple will be changed both in appearance and consistency. 
It assumes a brown to grayish color and becomes rather 
viscous. No appreciable coagulation will be found. Grad- 
ually the milk will be changed to a translucent, grayish- 

* The same is true in case of America (Russell). — W. 



102 MODERN DAIRY PRACTICE. 

colored, somewhat viscous fluid, which would hardly remind 
one of milk. It is further characteristic for the culture of 
these bacteria in milk that a lively generation of gas often 
takes place in the substratum. Carbonic acid seems to be 
the main gas generated. I have also observed a smell 
suggesting sulphuretted hydrogen. The presence of small 
quantities of alcohol and acetic acid may further be shown 
by distillation of the milk. 

Among the organisms belonging to this family I have 
only observed two varieties in Finnish milk — the one very 
thin and long, the other thicker and shorter. Neither 
seem to shun daylight particularly; they are both killed by 
a single rapid heating of the substratum to 158° F. (70° C). 
They seem to be found almost regularly in stringy milk;* 
they doubtless play a part in the formation of this milk, 
although they also seem to be assisted by others, e.g., of a 
lactic-acid bacterium appearing as streptococcus; the latter 
does not produce volatile acids, as is the case with other 
lactic-acid bacteria. 

2a. Bacteria Causi7ig Coagulation of the Casein. — 
Three different varieties found in Finnish milk are in- 
cluded in this subdivision. Of this number only one, how- 
ever, calls for special mention, since the other two seem to 
be comparatively rare. The third one is very common, and 
in my investigations has been found to appear in particu- 
larly large numbers in milk which had come in contact 
with manure-particles, etc. It is a short bacillus 
(1.5 X .5 fj), often thinner in the middle and with round- 
ed ends. Its power of locomotion is very pronounced. 
Thread-formed runners from the small colonies are no- 

* See " Saprophytic Micro-organisms in Cows' Milk," p. 27. 



BACTERIA COMMONLY FOUKD IN COWS' MILK. i03 

ticed on gelatine-plate cultures. The colonies soon sink 
in the dissolved gelatine ; they generally appear surrounded 
by a more or less fluorescent zone. In gelatine " stick " 
cultures of this kind the gelatine is dissolved in a funnel 
shape, and the surface then first fluoresces strongly, and 
later is covered by a greenish film. On agar-agar a green- 
ish-white deposit is formed. Even in beef -broth a green 
coloration is observed. This bacterium causes no acidity 
in milk, but produces a complete precipitate of casein by 
alkaline reaction (seldom by neutral reaction) ; a more or 
less pronounced disagreeable rotten smell, furthermore, ap- 
pears in the substratum. In many respects this bacterium 
seems to resemble Fliigge's Bacillus fiuoresceris Uqnefa- 
ciens. As mentioned above it is often met with in manure 
particles, especially if these are very moist. I have also 
found it in stagnant water. Sunlight and even daylight 
seems to kill the organism within a short time. 

2h. Bacteria Coagulating Casein and Stihsequently 
Peptonizing the Coagulmn. — This subdivision has not, 
according to my experience, many representatives in our 
country. The bacteria spoken of above as resembling 
the blue-milk bacillus belong here. Another represen- 
tative of this subdivision was found last winter in a sam- 
ple of milk from Helsingfors. The casein in this milk 
did not coagulate, but the whole milk assumed a jelly- 
like consistency, became fibrous and coherent, and turned 
a gi-ayish and afterwards a brownish color. Later on this 
jelly-like mass gradually dissolved. The bacteria causing 
these changes were isolated and found to be a long, 
staff-like bacillus which often appeared in coherent chains. 
Inoculated in sterilized milk it produced a strong alkaline 
reaction, and otherwise changed the milk as stated above. 



104 MODERN DAIRY PRACTICE. 

Quite frequently the so-called potato bacillus — Bacillus 
mesentericus vulgatus — is found in Finnish milk. This may 
easily be recognized by its active power of locomotion, its 
short, thick staff-shape, its strong peptonizing power, and 
its great inclination to build spores. I have also found 
represented in our Finnish milk the Duclaux Tyrothrix 
family, some species of which resemble in several respects 
the potato bacilli. The organisms belonging to this sub- 
division generally have spores possessing great tenacity 
of life; they easily withstand boiling temperatures. For 
this reason their presence in milk is very injurious. Ac- 
cording to Duclaux, the bacteria of this subdivision pro- 
duce two substances : the one which he identifies with ren- 
net precipitates casein, while the other again peptonizes it. 

This subdivision seems to be more numerous in milk 
produced in southern countries than in our northern milk. 
My investigations of South German and French milk 
would show this; and also the constant appearance of milk 
diseases, as red milk, blue milk, etc., which are caused by 
infection of bacteria belonging to this subdivision, in sam- 
ples of milk examined.* 

2c. Bacteria hanging Casein into Fermentation ivitli- 
out Coagulating It. — The final result of the activity in 
milk of bacteria belonging to this subdivision is the same 
as that of the families belonging to the last two sub- 
divisions, viz., a solution of the casein through decom- 
position. These subdivisions together form the group of 
bacteria called putrefactive bacteria by older bacteriologists 

* For a description of bacteria belonging to this subdivision see 
Scholl, "Die Milch," 1891, p. 43; Conn, "The Fermentations of 
Milk," 1893, p. 48; Freudenreich, " Bakteriologie d. Milchwirt- 
schaft," 1893, p. 45, etc. 



BACTERIA COMMOKLY FOUND IN COWS' MILK. 105 

— a term also used in the following pages for the sake of 
brevity. All these bacteria decompose albuminoid sub- 
stances and produce an unpleasant smell; the final prod- 
ucts in the substrata are carbonic acid, ammonia, and 
water. In the dairy they generally have an injurious in- 
fluence; some play a part in the ripening of certain kinds 
of cheese, however. They are of the greatest importance 
and value to the agriculturist in other domains, since 
they split up the complicated albuminoids of the manure 
into such substances as may serve as nutrients for cul- 
tivated plants. These bacteria are therefore especially 
numerous in solid and liquid manure, and their presence 
in milk shows that this has been contaminated with these 
substances. 

This applies especially to the bacteria included in the 
third subdivision. The more macroscopic impurities 
coming from the manure, the greater is the probability 
that these bacteria will appear in large numbers. The 
most common of them belong to the family Proteus (Hau- 
ser), and are characterized by a rapid power of locomotion; 
they are often supplied with cilia, and generally somewhat 
curved, staff-like bacteria. They seem to attack the casein 
of the milk directly without precipitating it, and dissolve it 
under decomposition. Although they do not develop spores, 
they are very tenacious of life. They can stand both pro- 
longed drought and a cold of - 4° to - 22° F. (20° - 30° C). 
The fermentation produced by these bacteria in milk gives 
it sometimes a bad and insipid, sometimes a bitter, taste. 
If the cream from such milk is allowed to grow old it will 
yield a rotten odor, and air-bubbles will form both in the 
inner portion and on the surface of the skim-milk. 

All the milk bacteria enumerated in the preceding are 



106 MODERN" DAIRY PRACTICE. 

aerobic, i.e., they form first of all in the presence of air. 
But anaerobic bacteria (i.e., such as cannot live in an at- 
mosphere containing oxygen) may also be found in milk. 
The examination of these is unfortunately attended by great 
difficulties. I have found a butyric-acid fermentation 
produced by anaerobic bacilli in two samples of milk, and 
in several other samples have found numerous anaerobic 
bacteria causing putrefactive fermentations. By an ordi- 
nary aerobic quantitative analysis only a very few colonies 
appeared in these samples ; this was contrary to the results 
of a preceding microscopic examination which showed that 
the milk was filled with numerous bacteria. The explana- 
tion of the apparent contradiction was of course that the 
bacteria found in the milk were largely anaerobic, and 
could not thus develop in cultures to which the air had 
free access. 

Other Micro-organisms in Milk. — The short enumera- 
tion of the injurious bacteria of milk given in the preced- 
ing only includes the bacteria proper. Other micro-organ- 
isms resembling the bacteria are also found in milk, 
that may influence its quality. Among these the yeast- 
fungi may be mentioned. They demand in the main the 
same conditions of life as the bacteria, are somewhat larger 
than these, and oval-shaped. They multiply through bud- 
ding (Fig. 12), i.e., in the manner that cell-buds project 
from one or both ends of the round cell. This gradually 
grows until the new cell reaches the size of the mother-cell, 
when it either breaks off from the latter by a cross- wall, or 
at once begins to form new buds. 

The yeasts appear comparatively seldom in milk, and 
only a very few forms are able to cause fermentations in 
this medium, and thus injure its quality. I have examined 



BACTERIA COMMONLY FOUND IN COWS' MILK. 107' 

the relation of a large number of different yeasts in this 
respect, and found that only two of them may be consid- 
ered as enemies of the quality of the milk. These produce 
lactic-acid fermentations, and also form alcohol in it in 
smaller or larger quantities. In " Saprophytic Micro-or- 
ganisms in Cows' Milk," pp. 34-36, 1 have characterized 
more fully these two organisms, which I have named Sac- 
charomyces lactis and S. acidi ladici. 

The latter yeast has several times been found by me in 
Finnish milk, both in milk from the Kuopio and the 
Joensum region, and in samples coming from Borgaa. 

Besides bacteria and yeasts, molds often appear in milk. 
We see mentioned in many text-books that the milk has 
a special mold, Oidium lactis. As a matter of fact, how- 
ever, we very often find organisms in the milk which long 
have had this name in bacterial science; they are especially 
found in milk left to sour in wooden pans. Every sample 
of sour milk of this kind which I have met with has been 
strongly infected by oidium lactis. The fact seems to be, 
however, that several different moulds hide themselves 
under this name, and that oidium lactis only signifies a 
certain stage of development with different moulds— a stage 
when they all have about the same appearance. They ap- 
pear to the naked eye as a fine, white, velvet down on the 
milk; under the microscope they appear like ramified 
threads separated by numerous cross walls. We shall in a 
later chapter return to the action of these moulds in the 
milk. 



CHAPTER IV. 
CLEANLINESS IN BUTTER AND CHEESE FACTORIES. 

The sources of infection of the milk while kept in the 
stable and during the transportation to the factory have 
been described in the preceding. We shall now consider 
the dangers of infection threatening the milk during its 
further treatment in the factory. The necessary cleanli- 
ness and care in receiving, weighing, and straining or 
keeping the milk in the vats are as a rule observed in the 
modern dairy industry. It may be in order, however, to 
call attention to some points in which this principle is 
occasionally violated. 

Admittance to Factory. — To begin with, the butter or 
cheese maker ought to take charge of the milk at the door 
of the factory, or at least at the door of the separator or 
milk-room. Farm hands or drivers should not be admitted 
into the creamery direct from the work in the barn. Yet 
we find that in nearly all creameries in our country, 
and not seldom in foreign countries, they are at liberty 
to visit any room in the factory. I have seen milk- 
drivers pour the milk into the separator-vat, change 
skim-milk cans, etc. It is not difficult to prove that 
dusty drivers carry legions of the infectious organisms of 
the milk with them into the factory, and in their move- 
ments clouds of dust charged with fermentation spores are 

set in motion. 

108 



CLEANLINESS IN BUTTER AND CHEESE FACTOEIES. 109 

Clothes of Factory hands. — That the factory hands 
themselves must keep clean in the most scrupulous man- 
ner is a principle agreed to by everybody in theory, but 
not always duly followed in practice. It is not fastidious- 
ness to insist that factory hands should appear dressed in a 
white, easily washable costume, for only in this case can we 
feel certain that they go at their work in a neat way, and 
that their clothes may not be the cause of infecting the milk 
or its products. Furthermore, it cannot be considered un- 
reasonable to require that persons working with milk or milk 
products to wear a white cap, as it is well known how easily 
hairs, etc., may loosen from one's head. The small coquettish 
caps placed on the back of the head, which are seen in some 
model dairies at expositions, do not accomplish the object 
sought.* 

It is often objected that it is impracticable for fac- 
tory hands to wear white costumes, as these soil so quickly, 
for which reason gray or blue-striped clothes are recom- 
mended. In my opinion this objection shows in the most 
striking manner that white clothes alone ought to be used 
in butter and cheese factories, for any dirt on them is 
noticeable. The first condition for keeping absolutely 
clean is, of course, that filthiness may be observed and im- 
mediately removed, thus preventing its spreading. 

Changing Clothes. — A question which sometimes agi- 
tates the owners of factories is how often the factory-hands 
ought to change clothes. As a reasonable rule in this 
respect it is often stated that every factory-man ought to 
appear with clean washed clothes at least every Sunday 
morning. According to my experience from both Danish 
and Finnish factories, it is, however, impossible to keep the 

* In Europeaa creameries all lighter work and the making of the 
butter are usually done by women. — W. 



110 MODERN DAIRY PRACTICE. 

clothes properly clean for a whole week, no matter how 
careful a person may be. The only sensible rule in regard 
to the changing of wearing apparel is that clothes ought 
to be replaced by clean ones as soon as they become slightly 
soiled. It is in my opinion necessary that factory hands 
should have clean clothes every day and every hour in the 
week, and not only at the beginning of the week. 

A great difference may, as a rule, be observed between 
men and women working in creameries in regard to out- 
ward appearance. We often find that the men are negli- 
gent as to cleanliness in wearing apparel, etc., a condition 
which not seldom has led to sad results as regards the 
butter and cheese product. It is of course true that the 
fact that neatness in outward appearance is observed is no 
guarantee for cleanliness in general; but, on the other hand, 
it is always difficult, almost impossible, for a person 
negligent about his looks to observe cleanliness in other 
directions. It does not involve so much expense for factory- 
hands always to appear in white and clean aprons, sleeves, 
and caps, for while laundry expenses are increased, the rest 
of tlie clothes are protected by their use. 

Necessity of Clean Hands. — The attention of dairy and 
factory workers may furthermore be called to the necessity 
of keeping their hands carefully clean, as these very often 
come in contact with the milk, cream, and especially the 
butter. I found the following custom prevailing at a 
margarine factory in France: Before beginning work in 
which the men came in near contact with the milk or 
its products they had to present themselves before the 
superintendent, who then strictly examined them as to 
cleanliness, especially their hands. 

Through the bacteriological investigations of Mittmann 



CLEANLINESS IN BUTTEE AND CHEESE FACTOKIES. Ill 

and others it has been proved that the frequently appear- 
ing black dirt under the finger nails contains a large num- 
ber of different kinds of bacteria. The heat and moisture 
found there are very favorable to the growth of micro- 
organisms; they are highly fit to become brooding places 
for all kinds of bacteria. Bremer has even shown the 
presence of tubercle bacilli in the dirt under finger nails, 
and putrefactive bacteria may easily be found in it. 

The Cause of the " Factory Odor." — Leaving the factory- 
workers and turning our attention to the factory itself, it 
must first of all be stated that in most of them (in almost 
all older ones) the atmosphere met with is far from pure 
and sweet. It is heavy and moist, mixed with a character- 
istic odor which reminds one partly of sourness, partly of 
musty, rotting wood. This specific creamery (and cheese 
factory) odor is a nuisance in most factories. If we look 
around at the floors, ceilings, walls, and utensils we are not 
in most cases at a loss to ascertain the cause of this condi- 
tion. Fermentation hotbeds without number may usually 
be found, and large colonies of moulds may be seen, as well 
as thick dirt-spots on walls and ceiling, and bad-smelling 
pools on the floor; in many cases the drain-gutter also 
spreads an offensive odor. Where such bad conditions 
are not present, there are others, more hidden ones, giving 
rise to the foul atmosphere. It is only necessary to ex- 
amine the corners of the rooms, cracks in the floor and 
wall, crooks and crevices of staircases and thresholds, and 
the explanation of the bad condition of affairs will doubt- 
less be found there. 

The Use of Water in the Creamery. — A characteristic 
feature of modern creameries is the superfluity of water 
used in them; it is, e.g., considered proper at any time to 



113 MODEEN DAIRY PRACTICE. 

deluge the floor. Many and great advantages are obtained 
by an abundant application of water, but the same ad- 
vantages may, as we shall see, be reached in another 
way. The main object of this liberal use of water in 
creameries is to remove all kinds of fermentable fluids 
found on the floor and elsewhere. By this means the 
fermentation-germs are removed, and under otherwise 
proper conditions the end sought will also be reached. 
The other method for removing spilt fermentative fluids 
formerly followed by dairymen also led to good results, 
especially where the conditions in the creamery were some- 
what primitive, and where the floor was not perfect. As 
soon as some milk, whey, etc., was spilt on the floor it 
was carefully wiped up, and the place was rinsed with 
a small quantity of pure water which was then also 
wiped up. This method of procedure is directly opposite 
to the first-mentioned one, and according to this method the 
creamery ought to be kept as dry as possible. Excellent 
results are doubtless obtained by a careful observation of 
this rule. On account of the lack of fermentative fluids 
bacteria cannot infest the factory, and the air in the whole 
building is fresh and sweet. 

As already stated, this method was much thought of 
during the early days of rational dairying. Martens thus 
writes in 1869 in his book on the dairy-farms of Schles- 
wig-Holstein : " The drier the milk-cellar is kept in every 
nook and corner, the highest cleanliness being at the same 
time observed, the better the milk will be protected from 
souring. Any one considering this too insignificant a 
matter to deserve attention can never hope to make 
high-grade butter." It cannot be doubted that this 
method of fighting the bacteria " on the dry way," as it 



CLEANLINESS IN BUTTER AND CHEESE FACTORIES. 113 

were, is good, and it certainly would be a great advantage 
if it were introduced as far as practicable also in our 
modern creameries. It has been objected that the steam- 
ing so often applied in the latter makes it difficult to fol- 
low this method; but this difficulty may be obviated by 
removing the steaming to a separate building, or at least 
to a separate room in the creamery. The separator-room 
ought occasionally to be rinsed and even steamed, but also 
here an effort ought to be made to keep the floors and air 
dry; in the other creamery-rooms the floors should be 
kept dry in the daily work. The impropriety of putting 
the wash-room in between the creamery-rooms, as is the 
case in many creameries, is evident from what has been 
said, as well as for other reasons. 

If the rule is observed that the steaming and rinsing 
are to take place in a separate room, there is no reason 
why the floors and the air even in our modern creameries 
may not be kept dry. The other difficulties connected 
with this method are easily overcome; the same scrupu- 
lous care and neatness which formerly existed in the 
creameries is necessary. Strict cleanliness can very well 
be observed in this way, without the use of large quantities 
of water. In addition, regular and when necessary special 
scrubbings and washings of floor, walls, and ceiling must, 
however, also be made. 

The method now commonly adopted in our creameries, 
viz., to remove dirt, milk, etc., from the floor through a 
liberal rinsing with water, offers this advantage, that it 
places less demands on the creamery-hands than the 
other method. This assertion is, however, in my opinion, 
founded on a misunderstanding, which is very deleterious 
to the quality of the dairy products. It says that the 



114 MODERN DAIRY PRACTICE. 

creamery-man may be relieved from paying attention to the 
condition of cleanliness in detail; he has to see to it that 
the rinsing be made thoroughly, and the rest will then 
take care of itself. The first man in the creamery con- 
centrates all his efforts on the making of the butter, the 
running of the separators, etc., and the cleaning up and 
even the supervision of the same is left to his helpers, 
while he himself ought to care for and look after every- 
thing, and this first of all as far as the conditions of clean- 
liness are concerned. An abundant use of water in 
creameries places great demands on the condition of the 
creamery-rooms, as will be seen from what follows. 

We often find larger or smaller cracks in the creamery 
floors; these places are splendid culture-beds for all kinds 
of bacteria. I have amused myself by examining bacteri- 
ologically the fluid which stood in such cracks in the 
cement floor of a creamery. An astounding sight met my 
eye. The large number of species of bacteria and the 
immense number in which most of them were found ap- 
proached the incredible. No better object-lesson can be 
found than such a fluid, if it is desired to illustrate espe- 
cially, to what an extent an object may be filled with bac- 
teria. The fluid will, of course, contain micro-organisms 
in proportion to the quantity of milk remains contained in 
it. From what has been said it follows that the creamery 
floor, above all in a creamery where large quantities of 
water are used for washing, must be tight, and even with- 
out cracks and crevices. 

The Factory Floor. — These conditions are not filled by 
the cement floors generally used in our creameries. It is 
easily cracked by bruises, and holes and crevices are thus 
formed in them. I have often observed in creameries, 



CLEANLINESS IN BUTTER AND CHEESE FACTORIES. 115 

especially in frame buildings, that the layer of cement has 
loosened along the walls and the crack thus formed has 
been filled with a dark, moist mass, containing filth of all 
kinds, and of course bacteria without number. Cement 
floors are furthermore eaten up by lactic acid (sour milk). 
On account of all this they cannot be recommended in 
creameries where large quantities of water are used for rins- 
ing. The same holds true in regard to floors of limestone 
slabs; the slabs have rarely a suJBficiently smooth surface, 
and they often cannot be laid close up to each other. The 
custom to lay these slabs as closely as possible up to one 
another in loose sand, which is practised in many places — 
especially in foreign countries — hoping that the interstices 
soon will be filled with sand and dirt, must of course be 
absolutely condemned, for infection hotbeds are thereby 
created all over the floor. It is a better practice to imbed 
these slabs in cement so that the interstices become filled 
therewith. I have, however, observed in several creameries 
where such floors are found that the cement between the 
slabs is soon eaten up and gives way to large gaping cracks, 
that gradually fill up with a sticky, filthy mass. Wooden 
floors are still more to be rejected. Through the abundant 
washing they are kept constantly moist and are apt to 
soften and swell, after a while allowing water mixed with 
milk to run through into the ground, where a luxurious 
and injurious mould and bacteria growth is produced in the 
dark, giving off bad odors and forming a constantly threaten- 
ing source of infection for the milk. 

The only creamery-floor which in my experience fills 
the demands just given, and thus allows of a flooding of 
the floor, are those made of a genuine, natural asphalt. 
Such a floor is firm, impervious to water, will not crack, is 



116 MODEKN DAIEY PEACTICE. 

not attacked by acids, does not spread any odor, can stand 
changes in temperature well, is not cold to walk on, and 
may be easily kept clean. To all these advantages may 
also be added that asphalt floors are easily laid and also 
very easily and rapidly repaired. It will not be necessary 
to interrupt the regular work in the creamery when such a 
floor is to be laid. If we begin laying the floor at noon 
immediately after the day's work is done, even the largest 
floor may be entirely done before .the milk comes in the 
next morning. 

The only disadvantages of asphalt floors in creameries 
is that asj)halt is dissolved by oils which may drop from 
the machinery, and that it becomes soft and pliable under 
cans filled with hot water. These disadvantages may, 
however, easily be avoided by a little care. Dripping of 
oil ought in general to be out of the question with dairy 
machinery, and the softening of the asphalt through the 
effect of hot cans may easily be avoided by placing these 
on a wooden stand. 

It is important that the creamery floor be laid at an 
even slant so that water may drain off as completely as 
possible. In this respect the asphalt floors are also very 
serviceable; gutters may be easily made in them, and what 
I consider very important, the asphalt may be laid from 
the floor up on the wall at least two feet, so that the lower 
part of the latter may be impervious to water. By this 
arrangement the part of the wall most liable to become 
soiled may easily be kept clean through rinsing and wash- 
ing. The wall around the exit-hole in the wash-room 
should also be dressed with asphalt. 

In planning and building creameries the number of 
corners and crooks that cannot be easily cleaned must be 



CLEANLINESS IN BUTTER AND CHEESE FACTORIES. 117 

diminished as far as possible. Dark hiding-places under 
staircases, etc., floor-drains which cannot he cleaned in 
their whole length, and similar places where infection 
might start up, ought not to be found. By painstaking 
care in the planning and building of the factory we may 
easily succeed in securing these conditions for keeping its 
atmosphere pure and sweet. 

If a tight, smooth, somewhat slanting, acid-proof floor 
built as directed has been secured, as abundant quantities 
of water as may be wished for can safely be used in keeping 
it clean. But how many creameries in our country fulfil 
such conditions ? Many creameries have still wooden floors, 
or, worse still (in, fortunately, but few creameries), there is 
only a wooden floor under and around the churn W/hile the 
rest of the creamery has to do with a dirt floor. The in- 
numerable chances of infection to which the delicate dairy 
products are here exposed may be easily imagined. One 
might believe that the picture drawn applied to a past era, 
when dairying was still in its infancy; but such is unfortu- 
nately not the case. I have even found a separator put in 
a creamery with such a floor. Otherwise well-equipped 
creameries also often leave much to be wished for as re- 
gards the material and the grading of the floor. 

When the main creamery work is done, about 1 p.m. 
every day, all machinery and vessels as well as the floors 
are of course cleaned. The floor is not washed until all 
other cleaning is finished, when it is washed with 
plenty of water and swept up with a broom. Here and 
there, however, some water remains in holes, cracks, 
etc., and if we enter the creamery an hour later we shall 
find the air exceedingly moist, and perhaps pools of 
water still left on the floors. These pools are often filled 



118 MODERN DAIRY PRACTICE. 

with bacteria, especially if the washing was done carelessly 
so that milk remained in them. To avoid this incon- 
venience the creamery floor should be frequently washed 
with boiling-hot tvater, and the washing of the floor at the 
close of the daily creamery work should be followed by a 
similar treatment. The floor will then dry more rapidly, 
and there will be no standing pools of water — at least not 
to such an extent as by the method now followed. 

The great humidity of the air in modern creameries in 
connection with the heat usually incommoding them in 
summer-time produce conditions particularly favorable to 
bacteria and moulds. In many creameries we observe 
various kinds of colored mould vegetation on walls and 
under the ceiling. Even if spores and bacteria from these 
colonies do not often get into the milk they will easily 
infect vessels and apparatus with which the milk comes in 
direct contact. 

Creamery Walls and Ceilings. — It is often difficult to 
keep ceiling and walls properly free from these growths. 
If the creamery has stone walls they are usually plastered 
and kalsomined, and cannot therefore be washed; this is, 
however, decidedly a weak point. In model creameries 
made of brick I have seen some rooms dressed with white 
tiles, which of course did splendid service. The walls 
could be washed and scrubbed as often as desired. Such 
tile walls may, however, prove too expensive in first cost. 
Two other methods of dressing the walls are cheaper, and 
have given satisfaction. If the walls are plastered with 
cement, smoothed, and several times finished with water- 
glass, a waterproof wall is obtained that will stand rinsing 
and careful washing. Such a wall is not so good from the 
standpoint of cleanliness, however, as it is grayish, which 



CLEANLINESS IN" BUTTER AND CHEESE FACTORIES. 119 

in my opinion is a serious drawback, since dirt cannot at 
once be observed on it. Walls satisfactory also in this 
respect may be obtained by painting the cemented and 
smoothed wall with white oil paint; this, however, will 
come a little higher than applying a dressing of water- 
glass. Wooden walls may also be made very neat by being 
painted white, and are then easily cleaned. The ceiling in 
the creamery-rooms must likewise be kept free from dirt 
and bacterial growth ; they had therefore better be dressed 
in the same way as the walls. 

Airing of Apparatus. — All woodwork in the creamery 
should be well painted. As often as practicable all loose 
wooden utensils ought to be carried outside into the open 
air and sunshine, to be dried and ventilated. In some 
creameries many utensils are unnecessarily massive and 
clumsy, making it difficult to carry them outside. The 
creamery-hands therefore soon grow tired of handling 
them and leave off the airing process, the result of which 
will soon be seen, however. I have often in Finnish cream- 
eries met with large working tables which have had 
colonies of molds and bacteria on the outside; having never 
had a chance to dry properly in the open air they were soon 
attacked by bacteria. In many creameries large and heavy 
boxes for cooling the butter are now being introduced; the 
small cooling boxes previously used were, in my opinion, 
considerably better, for the reason given. Water-soaked 
and rotting wood ought never to be found in butter or 
cheese factories. I suppose it is from such wood that the 
peciiliar factory odor largely arises. 

Ventilation of Factories. — In order to avoid the heat 
in the factories in summer-time the sun is usually shut 
out by blinds or curtains at the closed windows. The 



120 MODERN DAIRY PRACTICE. 

heat is certainly diminished in this way, but at the same 
time the creamery loses the disinfecting influence of sun- 
shine and daylight; the darkness produced is favorable to 
the bacteria and the ventilation is checked. Awnings are 
in some ways preferable, as the windows may then be 
kept open and a draught created. Many creameries are 
not ventilate during the day, but only during the cool 
evening and night. This method cannot, however, be 
recommended, since the air purified by sunshine and day- 
light is especially wanted. By ventilating only during the 
night a moist atmosphere is let into the creamery, produc- 
ing a wet coating on walls and ceiling. A certain coolness 
is obtained in this way, but it is bought altogether too 
dearly. A cool atmosphere may be produced in the 
creamery, e.g., in the same way as in breweries — by means 
of refrigeration machines producing cold and dry air. An 
apparatus which I have seen used in a small brewery, and 
which ought to be adapted to creameries, is the Lufthulil- 
apparat, patent Honerla. It is simple and easily worked; 
by means of a fan the air is forced into a funnel-shaped 
iron vessel where the cooling material (ice) is kept. The 
lower part of the vessel is divided into several compart- 
ments by shelves, between which the melted water runs 
down and the air rises up toward the ice. The air is thus 
comparatively cold when it reaches the ice, and a too rapid 
melting is avoided. If the ice be mixed with one-tenth 
part of salt, the cooling becomes still more effective. The 
apparatus is comparatively cheap (about $125). 

As the creamery-rooms may be kept properly cool by the 
use of this or similar apparatus, it is not necessary to venti- 
late less on account of the heat. The admission of large 
quantities of pure fresh air into the creamery-rooms is one of 



CLEANLINESS IN BUTTER AND CHEESE FACTORIES. 121 

the best means of working against the spreading of factory 
odor. All rooms ought to have ventilators, preferably 
both at the floor and the ceiling, and should be supplied 
with large windows which may be opened. 

The effort to keep the air in the cheese or butter fac- 
tories pure may be made very difficult and sometimes even 
impossible by an irrational arrangement of the various 
rooms in the factory. We find in many places that, e.g., 
the cheese-room is directly adjoining the churning or 
separator-room, although it is plain that the very bacteria 
active in the ripening of the cheese are the worst enemies 
to the keeping quality of the milk and butter, and may 
easily infect the adjoining rooms. We often see even the 
engine-room, with its atmosphere filled with soot and odor 
of oil, directly joining the separator-room; and frequently 
we find the room of the creamery-man opening into the 
milk-room. Bad arrangements of the rooms may plainly 
be fatal to the products made there, and, like a secret dis- 
ease, all the time prevent the business from paying. 

The Surroundings of the Factory. — In connection with 
the question of the necessity of fresh air stands the rule 
that every factory ought to have neat surroundings, a 
rule against which nearly every factory in our country 
sins in one way or another. In order to obtain purer 
air in the factory through ventilation it is, however, essen- 
tial that the air outside be purer than that inside. In 
spite of this but little care is in most cases taken of the 
many conditions which may infect the air in the vicinity 
of the factory. A few examples will illustrate the truth 
of this statement. 

Drainage. — What is the usual manner by which the 
wash and drain water when once outside of the creamery 



122 MODERN DAIRY PRACTICE. 

wall is prevented from stagnating and spreading bad 
odors ? In numerous instances no effort whatever is made 
to prevent it. In the worst cases slop-water is allowed 
simply to run under the floor and from there spread odors 
and infectious bacteria by the million. At other factories, 
again, it is left to stagnate just outside of the building and 
even dry off there, which of course causes the soil to be 
mixed with enormous masses of bacteria; when the wind 
sets the air in motion immense quantities of infectious 
matter gain access to the factory through windows, venti- 
lators, and doors. This immigration of bacteria from the 
outside may also take place in other ways. According to 
my observations, many bacteria especially injurious to the 
quality of the milk usually thrive in such stagnating factory 
slop-water. I have found species of tyrotlirix in such water, 
and also other of the putrefactive bacteria enumerated in 
the preceding chapter. 

The proper drainage of the slop-water is therefore of 
the greatest importance. Sub-earth sewers are in most 
cases to be rejected, since it is almost impossible to keep 
them properly clean. Only in cases where they can be 
properly cleaned by steam ought they, in my opinion, to be 
tolerated. Open sewers seem better, being more easily 
cleaned and watched. In the Danish bill concerning 
Co-operative and Proprietary Creameries (1888) it is speci- 
fied that "the slop-water is to be conducted from the 
creamery by paved or cemented gutters or glazed tile with a 
sufficient fall, to water-proof brick cisterns situated at least 
100 feet away from the creamery building, its well, and other 
buildings, provided they are occupied." " The cisterns must 
be cleaned and disinfected according to the further direc- 
tions of the inspection committee " (Sanitary Commission). 



CLEANLINESS IN BUTTER AlfD CHEESE FACTORIES. 123 

Location of Factories. — We see the proof of how poorly 
is understood the importance of the proper removal of 
drainage water for the successful conduct of the creamery 
business; in creameries being situated so as to make it im- 
possible to get rid of the slop-water without great expense. 
At such places as these no creamery should of course ever 
have been built. It is evidently absolutely impossible to 
keep the air pure and fresh in a creamery located near 
a barn yard or a hog pen. It is not so generally under- 
stood as we a 'priori should suppose, however; for here 
and there we find creameries whose location testifies to 
the ignorance of the owner in regard to this simple 
point. In the Danish bill just mentioned the distance 
required between the creamery and hog-pen is at least 50 
feet. Another mistake often made in locating a creamery 
is to place it at a lower point than the barn and manure- 
pile. On a dairy farm in our country I found, e.g., that 
the liquid manure drained off alongside the creamery, 
the ventilation of which was largely from the side where 
the drainage went. 

Even at factories where such glaring mistakes as those 
mentioned cannot be found, there is often one thing or 
another to criticise concerning the location. We thus 
often see the factories erected close up to the highway, 
from which dust clouds during the summer are scattered 
by teams and wagons. That a serious infection of the 
milk may arise from road dust is plain from the fact given 
by Maggiora that one gram of road dust {^-^ of an ounce) 
at Turin usually contains not less than 78 millions of 
bacteria. By investigations in our country I have never 
obtained as high figures, but my analyses have also shown 
that road dust contains immense quantities of bacteria. 



124 MODERN DAIRY PRACTICE. 

and I have found among these such as may injure the 
keeping quality of the milk. If a factory is located too 
near the roadside it is furthermore impossible to under- 
take the very necessary airing of utensils — a disadvantage 
which is by no means of small importance. 

It is, however, absolutely necessary to be able to reach 
the factory with teams. To avoid infection through dust 
the road up to the factory should be paved, and during hot 
days sprinkled and swept. It is greatly to be recom- 
mended to plant trees and keep a lawn around the factory. 
Close up to the factory there must not be tall trees, how- 
ever, as they will throw too much shadow, and prevent the 
light from properly purifying the factory air. Large 
groups of shrubs keep the ground moist, and if near the 
wall will produce rot and moldiness. A small, neat, orna- 
mental garden with old linden trees and some groups of 
flowers and shrubs here and there has this further advan- 
tage, that they not only increase the feeling of well-being 
of the factory hands, but also to a great extent sharpen 
their eye and sense for neatness and good looks. 

It is very difficult to keep a factory clean for any length 
of time in a dirty and poorly kept location: even if 
it is nice-looking and neat when built, so that it forms a 
real oasis of cleanliness among the disorder of the sur- 
roundings, it will pretty soon be impossible for the factory- 
hands to keep it so. Their eye for neatness and cleanli- 
ness will be gradually dulled, the fight against filth be- 
come more and more hopeless every week, and finally they 
meet and become accustomed to slovenliness in the factory 
itself. 

The Farm Dairy. — On many farms the dairy house is 
also used for other purposes than those for which it is 



CLEANLINESS IN BUTTER AND CHEESE FACTORIES. 125 

intended. I need hardly mention the mistake of using 
it for the storage of all kinds of food articles, as is the 
custom at many smaller farms ; these fill the air with the 
smell of food, which is easily communicated to the milk; 
with the articles of food, molds, dust, etc., are furthermore 
often brought into the dairy. 

A mistake of similar nature, which we are surprised to 
find also at many large places and which cannot be too 
strongly condemned, is that the washing takes place in the 
dairy. The dairy stands vacant for several hours every 
day, but if it is used for washing and steaming of clothes 
during the interval it cannot be properly dried out and 
aired before the dairy work again begins. And what is 
still worse, by using the dairy for this purpose a great 
deal of dirt and infectious material is brought into the 
dairy. There can be no doubt that typhoid and other 
disease bacteria have in this manner found their way into 
the milk. It must therefore be pronounced a gross mis- 
take in the dairyman if he permits the use of the dairy 
for this purpose. 

Disinfection of Factories. — In spite of all care and pre- 
cautions the bacteria will sometimes get the upper hand 
in some butter and cheese factories. In well-conducted 
factories this ought never to happen, but many of them 
are so arranged and equipped that it is impossible to ob- 
serve the rules of cleanliness in all respects in them. At 
such places where the bacterial growth cannot, then, be 
checked by ordinary means, it is necessary to fight the 
bacteria directly by arranging a disinfection of the factory 
or parts of it. We note in this connection that in dairy 
practice disinfection is often confounded with deodoriza- 
tion. It is not sufficient to destroy the odors which putre- 



126 MODERN DAIRY PRACTICE. 

factive and other fermentative processes produce in the 
creamery, but the bacteria themselves must be killed or 
their development and reproduction must be checked. 
Disinfection must therefore be considered far more im- 
portant than deodorization; the latter cannot, however, be 
neglected in the dairy practice, for dairy products, especially 
milk, are extremely sensitive to all odors. 

On account of this sensitiveness a good many disin- 
fectants, as carbolic acid, chloride of lime, etc., cannot be 
used for factory disinfection. Nor is it advisable to make 
use of poisons, as corrosive sublimate, in the disinfection 
of a butter or cheese factory, although these are very 
effective. 

Lime is used at several factories as a disinfectant, 
especially in case of acidity in milk utensils, etc. The 
disinfecting quality of this substance is, however, compara- 
tively small. Liborius concludes from lengthy investiga- 
tions that lime-water checks the development of micro- 
organisms, but cannot destroy them completely. Migula 
recommends to disinfect the yard outside the factory, floors, 
etc., by a repeated sprinkling of a freshly prepared solu- 
tion of slaked lime. 

Chloride of Lime is applied in breweries for this pur- 
pose, but both on account of its strong odor and its cost it 
will not be found adapted to creameries. Vitriol of zinc 
is, on the other hand, a very suitable disinfectant; it is re- 
ported to kill bacteria, and is also cheap. Other vitriols, as 
copperas and blue vitriol, may also advantageously be used, 
since they not only destroy bacteria, but prevent the rise 
of bad odors in the creamery. On account, of its poisonous 
character blue vitriol must be applied with care; copperas 
is cheap. Alexander Miiller recommends a preparation 



CLEANLINESS IN BUTTER AND CHEESE FACTORIES. 127 

made at Meyer & Riemann's chemical factory in Hamburg 
for application in creameries, containing 

Sol. iron sulfate 63^ 

Iron oxide 17^ 

Chem. combined water 20^ 

This powder is mixed with about 20 parts of water in a 
wooden pail, the mixture stirred and used after standing for 
a while, until the precipitate does not color the water yel- 
low or until the water no longer gives a distinct taste of 
ink. After having been well washed the floor is sprinkled 
with the mixture by means of a broom, and then rinsed 
with pure water. If the sewer-pipes and sewer-boxes are 
not deodorized through the action of the disinfecting 
fluid, some of the vitriol is sprinkled in them in solid 
form. In applying this chemical it may be noted that 
clothes or wooden materials with which it comes in contact 
will be colored brown from the iron in the liquid. 

Clilorin Gas may be applied for deodorization as well 
as for disinfection; potassium permanganate if however, 
to be preferred, and does splendid service. If substances 
possessing bad odor or taste are dipped into a weak solution 
of permanganate they will be freed from these undesirable 
qualities. The substance is entirely harmless, but is un- 
fortunately comparatively expensive. 

Water for Factory Purposes. — As is apparent from the 
preceding, water plays an important part in the manage- 
ment of the dairy business, and it may therefore be in 
order to further explain the conditions which influence its 
quality. 

If sufficient quantities of spring-water or good well- 
water are at hand it is comparatively easy to keep the 



128 MODERN DAIRY PRACTICE. 

creamery clean. But, especially during the spring floods, 
many of our factories have to be satisfied with an impure 
water, rich in micro-organisms which may directly con- 
tribute to the infection of the factory. 

As we have seen before, water is generally an excellent 
nutritive medium for a large number of bacteria, which 
thrive the better in it the more it is polluted with organic 
substances and the less it is exposed to the air. We often 
see brick-laid wells covered so that ventilation is rendered 
entirely impossible. I have heard complaints of the quality 
of the water at every factory where I found this was the 
case. In the Danish bill for Co-0]3erative and Proprietary 
Creameries previously mentioned it is stipulated that the 
wells of the creameries should be located in such a way as 
to prevent impure water from flowing into them. New 
creameries are to be located only where plenty of good 
water may be obtained. 

The solid particles and impurities found in the wells 
seem to affect the bacteria content of the water. It has 
been proved by special investigations that bacteria in wells 
multiply best in the immediate neighborhood of solid 
matters, even if these are as unfit for nutrients as stones. 
A properly-kept well ought therefore to be free from all 
unnecessary solid substances. It is further of importance 
that the well be not long left unused. The best way to 
keep the water pure in a well is of course to empty it as 
often as possible. Heraeus says on this point: The best 
well may, if used only a little or not at all, yield water with 
thousands of bacteria capable of reproduction in every 
cubic centimeter, and the poorest well may be so improved 
by continual pumping that its water will contain but few 
bacteria. 



CLEANLINESS IN BUTTER AND CHEESE FACTORIES. 129 

The bacteria content of well-water depends to a 
large extent on its origin. If it comes directly from the 
surface it will, especially during the hot season, be very 
rich in bacteria, since surface-water generally goes through 
fields, roads, and other places rich in bacterial life. In a 
good many of our factories this danger of surface-water 
leaking into the well has not been realized. Such water 
may in several creameries run directly into the well or 
down through the leaky woodwork; this explains why 
many creamery-men complain that they cannot use the 
well-water after a heavy rain. 

Even if the surface-water does not run into the well, 
the water may contain bacteria in large number, according 
to the stratum of the earth from which it is derived. 

The earth acts on the whole as a filter, retaining the 
bacteria. We therefore find the largest number of such 
organisms in its upper layers. In the surface layer of 
sandy soil (in Berlin) Frankel found 45,000-350,000 bac- 
teria per cubic centimeter, while Keimers in the surface 
layer of a clayey soil (in Jena) found 160,000-2,500,000 
per cubic centimeter; both investigators ascertained that 
the largest quantity was not found directly on the surface, 
but a little below the same — a fact which is perhaps ex- 
plained by the fatal action of the light on the surface bac- 
teria. From maximum at a few inches below the surface 
the bacteria content of the soil decreases rapidly as we go 
down. Frankel found only 200-2000 bacteria in soil 
three feet deep, and four and a half feet below the sur- 
face the soil was generally free from bacteria. In Jena 
absolute sterility of the soil does not appear until at a 
depth of six feet. These facts corroborate the observation 
made by both investigators mentioned, that the deep 



130 MODEKN DAIRY PRACTICE. 

water proper is always free from bacteria. Frankel's in- 
vestigations show that this is the case even where the 
water is derived from strata of the earth under highly 
polluted places. Artesian well-water is therefore as a rule 
sterile. 

The water in a creamery well ought of course prefer- 
ably to come from deep-soil layers. By digging a deep 
well another advantage is secured from the fact that the 
deeper the layer from which the water comes the colder it 
naturally is, and, as is well known, a low temperature will 
check the bacteria to a large extent. In comparing the 
raj)idity in the development of the same kind of bacteria 
from the upper strata of soil and from lower strata 
Eeimers found that the latter showed a considerably slower 
development ( Wachsthumsverlangsamung) than the former 
— a relation which appeared the sharper the deeper the 
well. 

In case of doubt whether the water available in a 
creamery is fit for use, it will not do to make only a chem- 
ical examination, but it must also be analyzed bacteriolog- 
ically. The difficulty with the latter examination is, that 
the sample must be analyzed as soon as taken. It cannot 
therefore be sent away for bacteriological examination, but 
the bacteriologist himself must take the sample and begin 
the analysis at once. If the bacteria in the sample get 
time to increase before the examination is made, it will 
not be possible to find the original bacterial content of the 
same. Owing to the fight between the different kinds of 
bacteria mentioned in the preceding chapter, the true rela- 
tion between the different forms can then, furthermore, 
not be ascertained — a point which is of course important 
in judging the applicability of the water. Heraeus fixes 



CLEANLINESS IN BUTTER AND CHEESE FACTORIES. 131 

as a standard for good drinking and well-water that it 
must not contain more than 500 bacteria capable of de- 
velopment per cubic centimeter. Plagge and Proskauer 
consider the upper limit 300 per cubic centimeter, while 
others place the standard still lower. 

The milk and its products often come into most inti- 
mate contact with water in the factory. Small portions of 
water will remain in every can, in the churn, in vats, on 
the worker, etc., so that the milk throughout its handling 
and manufacturing may be infected by bacteria found in 
the water. It will not therefore be surprising that we have 
dwelt at length on the importance of the quality of the 
water in the factory and the care of the well. 

Purification of Water. — It would of course be preferable 
to entirely remove the bacteria from the water to be used 
in the factory, but this would be too expensive. Breyer's 
" micro-membrane filter " is recommended by several parties 
for use in factories and is said to deliver sufficient water. 
The water is in this apparatus filtered through specially 
prepared asbestos disks. Chamberland's filtering apparatus 
also performs this cleaning process very well, but the ca- 
pacity of the apparatus is generally much too small to be 
adapted to factory use. At all events it is so expensive to 
remove bacteria from the water by such apparatus that it 
will hardly be generally adopted in factories. 

It is, however, the duty of every factory-man to keep 
the water in the factory as pure and free from bacteria as 
possible. He must first of all see to it that the well fulfils 
fair demands in regard to the conditions mentioned, and 
that the water is always used as soon as pumped. By 
standing in the warm factory a far greater number of bac- 
teria may develop in the same than was originally found in 



132 MODERN DAIRY PRACTICE. 

it. In some cases it will prove of advantage to free the 
water from coarse impurities by means of a sand or animal- 
charcoal filter. A simple and practical water-filter has 
been constructed by Paasch in Horsens, Denmark. In an 
iron cylinder about three feet high and one foot wide were 
placed six different layers, viz., small pebbles, gravel, sand, 
charcoal, rusty bits of iron, etc.; the layers were sepa- 
rated from one another by means of perforated false 
bottoms. The apparatus is very easily cleaned and kept in 
order. 

The water used for rinsing vessels in which milk or its 
products are to be handled ought in one way or another to 
be made germ-free. If" allowed to evaporate in or on the 
utensils it leaves on them not only all visible impurities 
it may happen to contain, but also substances invisible 
to the naked eyes, as bacteria. The special treatment 
necessary for preventing infection by the water may, in 
my experience, be of two kinds. The more common way 
in dairy work is to sterilize the water through boiling be- 
fore using it; where boiled water cannot be used, fnelted 
ice-water with pieces of ice still floating in the same is 
often applied. 

Sterilization of Water. — Both these methods may be 
recommended for factory purposes. The boiling is done 
by heating water with steam in clean tin cans after finish- 
ing the other work of the day; the cans are then covered 
so that dust cannot get into them, and the water is cooled 
as rapidly as possible. The majority of the bacteria and 
spores found in it will be killed by this treatment, and the 
development and multiplication of the few surviving ones 
will be checked. 

Use of Ice-water. — The method of applying ice-water 



CLEAKLINESS IN BUTTER AND CHEESE FACTORIES. 133 

in dairy work must be spoken of a little more at length. 
Many investigators have proved that ice may contain a 
large number of bacteria. Frankel found ice from the river 
Spree to contain between 20 and 6000 bacteria per cubic 
centimeter. Ice from rivers and lakes close by cities and 
factories will contain a large number of bacteria; conditions, 
as whether the ice sampled was formed near by the shore or 
out in the open lake, at the surface or farther down, will also 
cause great variability in the results found by analysis. 

Bacteria in Ice. — Although we may find a considerable 
number of bacteria in ice under certain conditions, it is, 
however, a fact that every time water freezes its bacterial 
content is considerably diminished. Frankel's investiga- 
tions show this plainly. Water from the river Spree 
containing 6000 bacteria per cubic centimeter froze at 
10°-18° F. After two days one cubic centimeter con- 
tained only 1200 bacteria, and after nine days only 14. In 
another sample 3300 bacteria were found per cubic centi- 
meter at the beginning of the experiment and after three 
days' freezing only 20 bacteria in the same volume. A 
third sample, which was highly infected with bacteria, con- 
taining not less than 500,000 bacteria per cubic centimeter, 
showed only 36,000 per cubic centimeter after six days' 
freezing. The freezing is therefore a powerful means 
against the development of the bacteria in the water.* It 
is in reality of no great importance that absolute sterility 
cannot be obtained in the water in this way, as the bacterial 
content by this method will be extremely small, provided 
the water is not highly infected before the freezing. 

In the bacteriological analysis of ice which I have 
made I have obtained greatly varying results, according to 

* See foot-note on p. 134. 



134 MODERN DAIRY PRACTICE. 

the origin of the ice. In examining thick lake ice in the 
centre of a large block of ice the analyses proved it to be 
entirely free from bacteria. On the surface of this block, 
which was exposed to infection during the cutting, haul- 
ing, etc., an appreciable quantity was, on the other hand, 
found ranging from 20 to 400 per cubic centimeter. Only 
one inch deep no bacteria was usually found ; sometimes, 
however, a couple of bacteria colonies appeared on the 
gelatine plates in the bacteriological analyses. The block 
of ice was taken from the lake in March and hauled to an 
ice-house; the analyses were made in the following August. 
Even porous, soft ice has proved very poor in bacteria, 
sometimes entirely sterile, if it did not come from the 
surface layer. This was found to be the case in ice taken 
from a lake where no city or factory was situated. The 
results of analyses made of ice from the harbor of Helsing- 
fors were different. They showed that the water must 
have been very rich in bacteria before the freezing, for 
about two months after the harbor was frozen over, the ice 
contained between 360 and 3500 bacteria per cubic centi- 
meter. The material for these analyses was taken by 
myself from the ice in the harbor. No ice free from 
bacteria was found in this place.* 

* Russell {Med. News, Aug. 17, 1889) gives bacteriological analy- 
ses of ice from Mendota Lake (near Madison, Wis.). No factory 
is found on the shores of this lake, but it receives a good share of 
the sewage from about 15,000 people. The number of bacteria 
per cubic centimeter of ice varied greatly, viz., in 62 trials from 14 
to 1249, the average number being 270. The bacteria content of 
the lake water varied from 3 to 3167, the average being 684 per cc. 
About 60 per cent of the bacteria were thus lost by the freezing. 
Prudden {Med. Record, 31, 344 ; see loc. cit.) claims that 90 per cent 
are destroyed by freezing ; while Fraukel {Zeit. f. Eyg., 1, 308) has 



CLEAKLINESS IN BUTTER AND CHEESE FACTORIES. 135 

My investigations concerning the bacteria of ice have 
also proved another fact, which still more confirms my 
opinion that recently melted ice-water is to be preferred 
even to very pure well-water in the dairy work. The in- 
vestigations showed that in case of bacteria remaining in 
the ice for a long time their virulence, i.e., their power to 
develop their specific qualities, was greatly diminished. 
Their multiplication took place very slowly, and where the 
bacteria were made up of fermentation-starters, the fer- 
mentation developed considerably more slowly and less 
intensely than was usually the case. I also observed 
that some of the ice-water bacteria which did not show 
any fermentative power on the first inoculation cultures, 
after having later reached their normal conditions again 
possessed this power. The investigations were made both 
with lactic-acid bacteria and putrefactive bacteria. The 
former, which caused a complete fermentation in milk 
before the freezing by being kept for twenty-four hours in 
an incubator at 86° P. (30° C), were unable to produce 
even something like a similar characteristic fermentation 
in several days after having been inclosed in ice for two 
weeks. The phenomenon is analogous to that which 
Keimers (see p. 130) observed concerning the bacteria from 
the deep layers of the earth, and also to that shown by me 

shown that " while in some cases the loss may reach as high as 90 
per cent, it is ordinarily much less." 

Comparative analyses of white and of transparent ice, made by 
Russell {toe. cit.), show, as the average of 153 determinations, that 
the latter kind contained a smaller number of bacteria than the 
former ("snow-ice ") ; but in several cases a larger number of bac- 
teria per cc. was found in clear transparent ice than was found in 
any sample of snow-ice. — W. 



136 MODERN DAIRY PRACTICE. 

in 1888 concerning the behavior of the lactic acid bacteria 
after repeated inoculations in sugar-free gelatine.* 

Putrefactive bacteria appearing in the ice also showed 
a considerably diminished peptonizing power. By inocu- 
lating for a long time slightly virulent bacteria of this kind 
successively on new fermentable mediums I have again 
been able to awaken their fermentative power and gradually 
return the normal virulence to the organisms. 

Uses of Purified Water in Factories. In some cases boiled 
water had better be applied in creamery and dairy work, and 
in other cases recently melted ice-water had better be ap- 
plied, as will be apparent from the following examples : 

The last rinsing of milk vessels ought always to be 
made with boiling-hot water. By this we gain both that 
the vessel dries more rapidly and that the water in evapo- 
rating does not leave behind living bacteria. The same is 
true in rinsing the churn, butter-worker, and all other 
utensils coming in direct contact with milk, cream, or 
butter. 

Before the cream is poured into the churn the walls of 
the latter ought to be given the temperature proper for 
churning by the application of recently-melted ice-water. 
When the butter, as is often the case, especially in making 
" Paris butter," is to be washed in the churn we ought 
generally to use water of comparatively low temperature, 
according to the experience gained at several creameries. 
40° F. (4° C.) is considered the best temperature at many 
places. Water containing pieces of ice is well adapted 
to this purpose; the pieces of ice ought not, of course, to 
go into the churn. 

* " See Saprofyta mikro-orgaaismer i komjOlk," pp. 36-42. 



CHAPTEE V. 

MILK FOR CITY CONSUMPTION. 

It does not come within the range of this work to treat 
this subject exhaustively. I cannot refrain, however, from 
referring to certain phases of it, since we may then learn 
the manner in which milk is usually kept when intended 
for direct consumption, and will have an opportunity to ex- 
plain the causes of some difficulties which city people meet 
in their efforts to keep milk sweet. The treatment of the 
milk before it comes to the household plays, of course, an im- 
portant part as regards the question of its keeping quality, 
as may be inferred from the preceding. I want to impress 
on housekeepers, first of all, that they must not buy milk 
blindly : they themselves should investigate the conditions 
on the farm where the milk used in their household is 
produced. This is easily done where the milk is obtained 
from a farm in the town where they reside; but even if the 
milk comes from the country they should not neglect to 
inform themselves concerning the conditions of cleanliness 
in the stable. This is above all necessary to insure one's 
self against the spreading of contagion through the milk, a 
danger which has not been treated in this book, but which 
cannot be disregarded. Such an investigation is the only 
way in which a housewife can protect herself against ob- 
taining unclean milk. If the milk-producers were under 

137 



138 MODERN DAIRY PRACTICE. 

the special supervision of the consumers it would act 
highly beneficially and educationally for the whole milk 
business; with their naturally higher sense of cleanliness 
the housekeepers would be able to call the attention of the 
milkman to many conditions deleterious to the cleanliness 
of the milk that may not have come under his observation. 

Their influence is especially necessary for starting a 
reform regarding stables situated in small towns; accord- 
ing to my observations these are generally almost below 
criticism, as far as cleanliness is concerned. My investi- 
gations of the milk from different city stables have further 
verified this fact. 

On approaching such a stable we find stinking manure 
and other filthiness outside the door, and the air in the 
stable and around it as a result becomes intolerable, espe- 
cially on warm days. The stable air is often so bitter and 
sharp that it makes the eyes of the visitors smart, and 
when the door is closed complete Egyptian darkness reigns. 
This darkness has a bad influence on the keeping quality 
and paiatability of the milk, as is plain to every one who 
has studied the preceding chapters. Still more shocking 
than the accommodations are the animals in such a stable. 
They are usually dirty and unbrushed from horns to tail, 
and manure particles may be seen all over their bodies 
We readily see how these conditions will influence the milk 
produced by the cows. 

The filthy condition of many of these stables arise first 
of all, I suppose, from the fact that they usually are very 
narrow, dark, and poorly arranged, but other factors also 
contribute to the result; litter is expensive in cities and 
towns, and the cows are fed large quantities of concen- 
trated feeds, brewers' grains, distillers' slump, etc., which 



MILK FOR CITY CONSUMPTION. 139 

produce a very soft and stinking manure.* It is expen- 
sive to preserve cleanliness under such conditions; but, on 
the other hand, such farms pay better than those in the 
country, and their owners ought therefore to be willing 
to go to somewhat greater expense. It is deplorable, how- 
ever, that in most cases they do not even pretend to keep 
their cows clean. 

We saw before (see page 87) that a milk examined 
half an hour after milking on three consecutive days con- 
tained the following number of bacteria per cubic centi- 
meter: 730,000, 560,000, and 780,000. This milk came 
from a village cow-stable of the kind Just described; its 
taste was, strange to say, very good, and it gave the impres- 
sion of being unusually rich. But it very soon spoiled; 
although kept on a window-sill at a temperature of about 
45° F., it coagulated slightly and turned " off flavor" after 
only ten hours. The examination spoken of took place 
in April. Analyses of milk from similar farms gave also 
bad results, although the bacteria content was not as 
large as in the case mentioned. 

The explanation that such milk can be used in house- 
holds in spite of all it has gone through lies in the fact 
that it is rapidly consumed. It is delivered to the cus- 
tomers as soon as it is milked, and often consumed a couple 
of hours afterwards. 

* Soxhlet states {Munch, med. Woch., 1891, No. 19) that feeding 
stuffs causing frequent evacuations of a thin dung favor the con- 
tamination of the milk, since they make it more difficult to keep the 
cows clean ; to these belong sour distillers' slump, root leaves, dif- 
fusion chips, etc. The potato bacillus present in distillers' slump 
furthermore makes the milk liable to abnormal fermentations ; hay- 
dust contaminates the milk in a similar way. See also Auerbach, 
Bcrl. klin. WoehentcTir., 1893, No. 14.— W. 



140 MODERH DAIRY PRACTICE. 

• 

Coming now to the milk furnished by farms in the 
country, we find of course better conditions in many re- 
spects. We have here two different kinds of stables — 
primitive and comparatively modern ones. The former 
remind one in the main of the village stables just de- 
scribed, although they are a good deal better. The build- 
ing of the stable, the lack of windows, and some other 
conditions are similar in the two cases, but the cows in 
poor country stables are generally much cleaner than those 
in town stables. Litter is more plentiful in the country, 
and the feeding of the cows is seldom so intense as in the 
city. This superiority of old country stables is, however, 
only relative ; if we compare them with the modern stables 
in the country the judgment would be entirely different. 

I have only had occasion to analyze milk from such 
farms a few times. As already stated, a sample of milk 
produced in such a stable was very strongly infected with 
bacteria five hours after milking. 

We meet with better conditions and better results in 
examining the country farms equipped and conducted in 
a modern manner. Conditions are also here found, how- 
ever, which need improvement, as may be inferred from 
the description in Chapter II. 

The milk furnished to city households is not consumed 
until after a shorter or longer transportation. As the milk 
becomes more or less contaminated in every stable, it must 
be strained and cooled immediately after the milking. If 
the milk is properly cooled before the transportation it 
will not be necessary to cool it during the same, provided 
the distance is not too great: it need then only be pro- 
tected from being warmed which may be effected by plac- 
ing the milk-cans in double-walled boxes, the walls of 



MILK FOR CITY CONSUMPTION. 141 

which have been packed with dry shavings, saw-dust, or 
similar material. 

The milk should of course be delivered to the consum- 
ers as soon as possible after having been drawn; but in 
many cases it is impossible to so arrange matters as to 
bring it directly into their hands, and it is left at some 
"milk-depot" in the city. 

Milk-depots. — Fortunately the milk-depots in our larger 
cities, thanks to the vigilance of our health officers, have 
of late improved in many ways. Some features, however, 
need further examination and subsequent change. A milk- 
depot ought to be as neat, light, and clean as a creamery, 
and should have many of the facilities of the latter at its 
disposal. The salesroom should be arranged so that the 
customers never need come near the milk-room. The 
milk is to be cooled to prevent any bacterial development 
worth mentioning from taking place in the same. The 
temperature of the milk ought never to exceed 45° F. 
Sour and sweet milk must not be kept in the same room; 
nor should cheese or other articles of food be kept to- 
gether with sweet milk. If some milk is spilled it should 
immediately be wiped up. As regards the floor, the same 
holds true in the main as already stated concerning cream- 
ery-floors. Neatness must be everywhere. The supply 
of ice should not be scant or even entirely lacking, as 
unfortunately is no unfrequent occurrence in many milk- 
depots. 

Care of Milk in the Household. — When the milk has 
reached a city household it seems to be a general supposi- 
tion that it requires no further care. It is argued that 
if it is good it will keep; if it is poor and sours soon we 
change milkmen. This reasoning is, however, unjust to 



143 MODERN DAIRY PRACTICE. 

both parties concerned. It is fortunate that the milk in 
cities is consumed so soon, for otherwise the injurious re- 
sults of this careless treatment would oftener show them- 
selves. 

Milk kept in the dark in covered and unventilated 
cupboards often does not sour, but assumes an insipid, sick- 
ening, or bitter taste, and shows distinct signs of putrefac- 
tive fermentations on standing for a longer time. This 
led me to investigate why especially putrefactive bacteria 
gain the upper hand in such milk; and I found that the 
conditions of light are first of all the causes of it. 

Although bacteria, generally speaking, develop best in 
the dark, we observe in some a greater dislike to light than 
in others. Bacteria of milk may be separated in two dis- 
tinct groups, according to their behavior in this respect. 

1. Those that can stand daylight without injury. 

2. Those that develop only with difficulty in daylight. 
The lactic-acid bacteria belong to the former group, and 
the great majority of the putrefactive bacteria and the 
butyric-acid bacteria to the latter. 

If the milk-room is airy and well ventilated as well as 
light and clean, we can conclude with a great deal of cer- 
tainty, provided the milk has been properly handled at the 
farm, first, that a comparatively small number of bacteria 
is found in it, and second, that putrefactive bacteria are in 
the minority. The lactic-acid bacteria, which are practi- 
cally everywhere, will then thrive best, and keep the putre- 
factive bacteria in check — at least as long as the nutritive 
conditions are favorable. 

Sometimes a slight acidity in the milk can also be dis- 
covered by chemical reactions: this has arisen partly 
through the lactic-acid bacteria, which owing to their 



MILK FOR CITY CONSUMPTION". 143 

unusual powers of resistance can if only in a small degree, 
develop their specific qualities, and partly because bacteria 
forming other acids in the milk have been able to de- 
velop. Even some moulds which do not seem to have any 
special liking for the light play a certain part in these 
changes of the milk. 

Considering what has been said, we cannot be surprised 
that the putrefactive bacteria gain the upper hand in milk 
kept in dark, small, city cellars or pantries. 

One of the reasons why milk spoils so soon in old 
and poorly ventilated milk-rooms and depots is, that the 
infection is allowed to become more intense and thorough 
with every day, as the rooms are not thoroughly cleaned 
as often as necessary, and are never disinfected. A 
mass infection may therefore easily arise by the least 
motion in the room, and the fermentation in the milk will 
have a good start. To this must be added that the tem- 
perature in such milk stores and rooms is often very high. 
Whenever possible the milk ought to be kept on ice; but 
where ice is not available a too high temperature may be 
avoided by taking simple precautions, as, for instance, by a 
system of ventilation, by keeping the milk in cold running 
water, etc. 

One side of the question which cannot here be treated 
fully is, that milk kept under bad conditions may easily 
become dangerous to human health. I shall here only 
point out that the conditions favoring the development of 
the bacteria inimical to the keeping quality of the milk 
are also favorable to bacteria injurious to human health; 
in fighting the former we therefore at the same time coun- 
teract the latter. 



CHAPTEK VI. 
STERILIZATION OF MILK. 

We have seen in the preceding chapters that it is im- 
possible to obtain a product of absolute keeping quality by 
our common methods of handling the milk. It is well 
known that the comparatively poor keeping qualities of the 
milk cause great difficulties in its handling and sale, and 
efforts were already long ago made to preserve the same so 
that it could be better kept and more easily handled in the 
trade. 

The simplest and most natural method of preserving 
the milk has already been mentioned several times, viz., to 
cool the milk sufficiently. It is hardly practicable in the 
trade, however, as it is expensive and inconvenient con- 
stantly to surround the milk with a cooling medium. This 
is, nevertheless, the only way to preserve the milk without 
its losing its original qualities; all other methods cause 
greater or smaller changes in the chemical composition of 
the milk, its taste, appearance, etc. 

Use of Chemicals. — A method which has long been ap- 
plied and as long been objected to, is to add all kinds of 
antiseptics to the milk, salicylic acid, boracic acid, etc. ; 
these substances partly kill the bacteria themselves and 
partly prevent their growth; such milk is often sold as 
" improved milk," but ought properly to be called simply 
adulterated milk. 

144 



STEKILIZATION OF MILK. 145 

Salicylic Acid seems to be the more common chemical 
used for preserving milk. It has, however, serious disad- 
vantages. Not more than 75 centigrams per liter (about 
10 grains per quart) can be applied before its characteristic 
taste appears too strongly. By tho application of this 
quantity the coagulation of the milk is retarded, but its 
acidity increases. It is besides notable that the antiseptic 
influence of the salicylic acid appears best if the milk is 
kept at the temperature of 68° - 77° F. ; at 77° - 104° 
F., e.g., it can hardly be observed. Bersch states that by 
an addition of .1 to .2 gram of salicylic acid to one liter of 
recently-drawn milk it may be kept sweet for six days 
longer than it would if it had not been treated in this 
way. As regards the injurious effect of salicylic acid on 
human health, Kolbe claimed to have proved that this 
acid is excreted very rapidly from the full-grown animal 
body, for which reason no injurious accumulation is to be 
feared in consuming an article of food preserved with it; 
but the application of salicylic acid for the preservation of 
milk is at the present time condemned from a hygienic 
point of view. For this reason its use is, e.g., in France 
entirely prohibited as a preservative of food products. 

Borax and boracic acid also are often used for preserv- 
ing milk. As early as 1883, however, Forster warned 
against the application of these substances for the object 
mentioned, as even in small doses they exert an injurious 
influence on human digestive organs. Many other scien- 
tists, as Bersch and Duclaux, express themselves in the same 
direction. 

The addition to the milk of one or the other substance 
must always be considered an adulteration in case the 
consumer is not informed tliereof: for such substances 



146 MODERN" DAIRY PRACTICE. 

change the natural condition of the milk and hide its true 
quality.* 

Condensed Milk. — Another method of preserving milk, 
to which great hopes were attached in the past, is to pre- 
pare condensed milk in hermetically-sealed tin cans. About 
twenty years ago a large number of expensive and mag- 
nificent factories were erected for this purpose in various 
countries, but only comparatively few were able to operate 
for a long time. The products did not, as anticipated, prove 
of such quality that it could find a good market anywhere, 
for which reason they are now used only in cases where 
other milk cannot possibly be obtained, as for instance on 

* The indiscriminate use of preservatives in food articles ought 
to be prohibited by law ; this is especially urgent in case of such 
articles as milk and other dairy products, which in a large measure 
cuter into the nutrition of children and convalescents. Most Euro- 
pean countries long ago prohibited the addition of salicylic and 
boracic acid, and other antiseptics in food, e.g., Germany, Holland, 
France, Austria, Spain, Italy, etc. Mr. Hehner, the President of the 
Society of Public Analysts of England, in the November 1890 meet- 
ing of the Society, read a paper on Food Preservatives (see Analyst, 
15 (1890), p. 221), in which he forcibly sums up the question in the 
following paragraph : 

" We should work for the entire prohibition of all kinds of pre- 
servatives. It is time that we went back to natural food. I object 
to being physicked indiscriminately by persons not qualified to ad- 
minister medicine whilst I am in health. I object still more when I 
am ill. I object still more strongly to have my children physicked 
in their milk or their bread and butter. It is no consolation to me 
to know that the physic is not immediately fatal or not even violently 
injurious. The practice is utterly unjustifiable, except from the 
point of view of a dealer who wants to make an extra profit, who 
wants to palm off a stale or ill-prepared article upon the pub- 
lic."— W. 



STERILIZATION OF MILK. , 147 

long voyages, in mining districts, etc. That this industry 
at the present is not insignificant, however, is apparent 
from the fact that according to official statistics not less than 
520,000 boxes were exported from Switzerland during 1888, 
each one containing forty-eight one-pound cans of con- 
densed milk. The value of this export article was calcu- 
lated to be about half of the value of the export of Swiss 
cheese from Switzerland. 

Two different methods are mainly used for the prepa- 
ration of condensed milk. In the older one of these, 
adopted, e.g., in the factories in Cham and Guni of the 
Anglo-Swiss Company, sugar is added to the milk in the 
process of manufacture. The main features of the method 
are as follows : The milk is repeatedly heated to 158° — 
176° F. (70° - 80° C), and evaporated in vacuum-pans; 40 
to 50 grams of cane-sugar is then added for every liter 
(quart.) of milk. By this method the milk is sterilized and 
its water content reduced to only one fourth of the original 
bulk. The final product is a thick, syrupy mass containing 
all the nutritive components in the milk. Chemical analy- 
sis of this condensed milk shows its composition to be 23 
to 26 per cent water, 6 to 11 per cent fat, 8 to 10 per cent 
casein, 53 to 57 per cent sugar, and 2 to 3 per cent ash. 

In the other and later method for condensing milk no 
sugar is added, and the product does not therefore obtain 
the exceedingly sweet taste which makes the condensed 
milk prepared according to the former method objection- 
able to many persons. This method is applied, for instance, 
at the factory Schuttendobel near Hartzhofen in the Bava- 
rian Algauer Alps, and is described in the following man- 
ner: 

As soon as received the milk is cleaned from the dirt 



148 MODERN" DAIRY PRACTICE. 

contained in it by means of a separator, and is then evap- 
orated in a vacuum-pan till it contains 37^ of dry substance. 
The condensed milk is filled into tin cans by a special 
measuring and filling apparatus, and these are then sol- 
dered and heated in the sterilizer under steam-pressure. 
This method seems to possess many advantages over the 
first-mentioned one. The condensed milk is free from 
milk dirt, has no disagreeable sweet taste, and contains 
always the same quantities of water; it has therefore 
always the same consistency. 

As already stated, the condensed milk has not found 
application on the milk markets proper, although its keep- 
ing qualities have been all that could be wished for. Its 
consistency is too different from that of ordinary milk, and 
its price has been too high. The effort has therefore been 
made to preserve milk by sterilization without changing 
its physical properties. This sterilization of the milk may 
be effected in two different ways : first, hy filtration, and 
second, hy heating* 

Sterilization by Filtration. — Different kinds of mate- 

* I pass by the method proposed by the Frenchman Guerin to keep 
milk in a frozen condition. By this method the bacteria are certainly 
prevented from starting fermentations, but the method is not prac- 
ticable, since the milk imdergoes certain changes in freezing which 
decrease its application. [Notices occasionally appear in the agricul- 
tural press concerning the sale of frozen milk in foreign countries. 
In the Danish Landmandsblade (vol. 37, p. 305) the following 
item was thus given, the correctness of which I am not in position 
either to confirm or deny : " Frozen milk is an article of food of late 
years introduced to an appreciable extent in France and Siberia. 
The frozen milk is comparatively easily transported, will keep for a 
long time, and when melted is said to be as palatable as fresh new 
milk."— W.] 



STERILIZATION OF MILK. 



149 



rials have been used for filter for the purpose of steri- 
lizing fluids. Zahn used burnt clay, as did also Tiegel and 
Klebs. Gypsum was used by Pasteur and others, porce- 
lain by Chamberland, fayence by Gautier, and asbestos 
cardboard and plastic charcoal by Hesse and Breyer. All 
these substances easily take up the mechanical materials 
suspended in a fluid, and thus also the bacteria, on the re- 
moval of which the fluid will keep. 

As Zahn's experiments in my opinion in a very simple 
and plain manner illustrate the preservation of milk by 
filtration, I shall briefly describe his method of procedure. 
Into a porcelain tube glazed on the outside he fitted tightly 
a rubber stopper, in which a tube connected with an aspi- 
rator was placed. The apparatus was then sterilized. 
When cold, it was lowered into the milk 
and the aspirator opened. By means of 
this simple apparatus, shown in the accom- 
panying illustration, Zahn succeeded in 
sterilizing the milk. (Fig. 25). 

Several different kinds of apparatus for 
sterilizing fluids by filtration are made at 
the present time; none of these are fully 
practical, however; the most promising 
ones are the porcelain filters of Chamber- 
land's mentioned in the preceding, which 
act continuously and regularly. 

It is easy to sterilize milk in this manner, but unfortu- 
nately it is changed also in other ways by this method. 
Duclaux has thus shown through lengthy experiments 
that not less than nine tenths of the albumen content 
of the milk remains in the filter. The albuminoids are 
not really dissolved in the milk, but appear in it in an 




Fig. 25. 



150 MODERN DAIEY PRACTICE. 

exceedingly fine, suspended condition. The difference 
between the milk and the fluid passing the filter is so great 
that the latter hardly can be called milk. Its most nutri- 
tious constituent is gone. By this filtration the steriliza- 
tion of the milk is therefore obtained at the expense of its 
nutritive value. 

In the experiments which I have made in filtering milk 
by means of Chamberland's filter the fat globules of the 
milk have furthermore often caused difficulties, as they 
will not easily go through the filter at a rather low 
temperature, and usually clog its inner portion so that 
the cleaning is very difficult. The same must, of course, 
also be the case when other methods of filtration are 
applied. The method of sterilizing the milk through 
filtration must then, at least* in its present phase, be re- 
jected.* 

Sterilization of Milk by Heating. — Before entering on 
this subject it may be proper to state briefly the chemical 
changes which milk undergoes in heating. These changes 
are not noticed until the heating rises to about 185" 
F. (85° C), when a small separation of albumen may be 
observed as a white precipitate. Small quantities of 
casein also seem to separate at the same time. If the tem- 
perature is increased above 185°, the albumen will be pre- 
cipitated more heavily, and the power of coagulation of 
the casein will be decreased. A. Mayer states that this 
power is decreased even at 167° F. (75° C). If, however, 
the temperature of the milk is slowly raised to 167° F., yes, 

* While the apparatus mentioned are of no practical value for 
sterilization of milk, they serve in an excellent manner as water-fil- 
ters, and are extensively used as such, especially in larger cities, or 
where the drinking-water available is not above suspicion. — W. 



STERILIZATION OF MILK. 151 

even to 212° F., then cooled to about 86° F., and good 
rennet added in larger quantities than usual, distinct 
symptoms of coagulation will appear, although much slower 
than ordinarily. Not only are the albuminoids of the milk 
changed by a stronger heating, but the milk sugar also 
shows the influence of the heat. If a temperature of 185° 
to 200° F. acts on the milk for some time or at intervals, 
it will be easily noticed that it assumes a brown coloration ; 
this occurs through a formation of caramel in the milk, its 
milk sugar being partly decomposed. 

If the heating is carried farther, the symptoms men- 
tioned become still more noticeable, and at the same time 
the cooked taste, which was only slight by heating to about 
167° F., becomes more pronounced. At 266°-300° F. a 
coagulation of casein takes place, according to Hammar- 
sten, in a manner chemically identical with the coagula- 
tion through the addition of rennet. 

The sterilization through heating is in practice con- 
ducted in two ways: 1, hy boiling under pressure, and 2, 
iy ordinary boiling. 

The ormer method was introduced into practice by 
Nageli, who, at the Dairy Exposition in Berlin in 1879, 
published his experiences with the same. As the foremost 
spokesman of this method in practice, E. Scherff, in Wen- 
disch Buchholtz (Berlin), has made himself known, and 
Scherff's milk has of late often been spoken of. Ac- 
cording to his method of procedure the newly-drawn milk 
is poured into glass bottles, which are stoppered, and then 
heated under pressure at 248° F. (120° C.) for one to two 
hours. This method is old, and has long been known in 
science. The new in Scherff's method, which the in- 



152 MODERN DAIRY PRACTICE. 

ventor has patented in Germany, lies in the peculiar 
method of closing the bottles. 

Scherff's milk will keep beyond question ; both bacteria 
and their spores are killed by this treatment. But even 
by the application of this method the milk undergoes all 
kinds of changes, as is natural at such a high temperature, 
so that its usefulness is greatly impaired. The milk 
assumes a cooked taste, which often approaches that of 
burnt milk: and the color is often brownish, showing 
that a caramel formation has taken place. Munk even 
found that Scherff's milk had to be mixed with four 
times the customary quantity of rennet to effect a coagu- 
lation, and that this process took place more slowly than 
usual in spite of this liberal addition of rennet. 

The other method of sterilizing milk by heating is to 
boil it at ordinary pressure. Experiments were made 
in sterilizing milk by heating to 212° F. for two hours, 
but this method proved unsatisfactory, as no reliable 
sterilization was obtained. It has been found that spores 
of several bacteria will survive this process. The spores of 
the liay bacillus, which, as before mentioned, is often found 
in milk, are not killed by such a heating continued even 
for six hours. The spores of the hutyric-acid bacillus are 
so tenacious of life that they survive boiling from one to 
two hours. The same is true for Duclaux's TyrotJirix 
tenuis. 

This temperature having proved insufficient, experi- 
ments were made by heating the milk to a higher degree. 
Pasteur found that a single heating to 225°-227° F. is ordi- 
narily sufficient to sterilize the milk. Other investigators 
again state that it is necessary to heat the milk 230°-239° F. 
to make certain of complete sterilization. Other difficul- 



STEEILIZATIOK OF MILK. 153 

ties came in with this strong heating, however. The milk 
assumed a brown color and acquired a burned or boiled 
taste, whicL was generally objected to by consumers. 

Such milk cannot be used for baby-feeding. It is 
furthermore very expensive, and diflBcult to arrange for 
this heating on a large scale. It can only be done by 
means of a so-called autoclave, or by the application of salt 
solutions. It therefore proved impossible in many cases 
to apply high temperatures for the sterilization of milk. 

Through Tyndall's and Gay-Lussac's investigations we 
have learned, however, that sterility may also be obtained 
in liquids by application of lower heating by the so-called 
intermittent sterilizatio7i, which was already spoken of 
in the Introduction (see p. 15). Hueppe seems to have 
been the first one to apply this method for sterilization of 
milk. He stated that it was only necessary to apply a 
temperature of 167° F. (75° 0.) for half an hour for 
five consecutive days. It has been found, however, that 
this method is not al^vays reliable. Only where the re- 
sults obtained can be controlled, as in laboratories by 
testing in an incubator or similar apparatus, can they be 
relied on. In my experiments, cultures of certain species 
oi potato bacilli in milk have stood such a treatment with- 
out appreciably losing their vitality. We know bacteria 
which develop well at about 158° F., — a fact sufficient to 
shake our faith in the reliability of a method of steriliza- 
tion of the kind mentioned. This also shows the reason 
why different scientists have come to such different re- 
sults in their investigations of this subject. One states 
that milk may be sterilized perfectly by repeated heating 
to 167° F., and another that a considerably higher tem- 
perature must be applied. The difference of results comes, 
of course, from the fact that different bacteria were found 



154 MODERN DAIRY PRACTICE. 

in the samples of milk investigated. Hueppe has later pre- 
scribed that the intermittent sterilization of milk takes 
place best by exposing it to live steam at 312° F. during 
the first day for an hour, and during each of the follow- 
ing two or three days for twenty to thirty minutes. As 
already stated, a separation of the albumen of milk takes 
place at this temperature, its behavior toward rennet is 
changed, and an almost imperceptible change in some of 
the milk-sugar takes place. 

The intermittent sterilization applied in laboratories 
has also been introduced in practice for the preservation 
of milk by the Norwegian Chr. Gerhard Dahl of Dram- 
men, who succeeded so well in this that at the last Paris 
Exposition he could show milk several years' old prepared at 
his factory. This milk is said to have been very palatable, al- 
though it possessed a distinctly cooked taste, which, however, 
according to a statement made by a visitor at the Exposition, 
was no more pronounced than that of ordinary boiled milk. 

Dahl describes his method in the following manner in 
the letters-patent granted in Germany November 14, 1886 
(quoted from Molkerei-Zeitung) : 

The method of condensing the milk consists in (1) cool- 
ing the newly-drawn milk to 50°-64° F. (10°-15° C); (2) 
filling the milk into cans; (3) air-tight stoppering; (4) heat- 
ing of the cans to about 158° F. (70° C.) for about one and 
three quarters of an hour; (5) cooling to 104° F. (40° C.) for 
one and three quarter hours, and then (6) rapid heating of the 
milk to 158° F. (70° C); (7) repetition of these three pro- 
cesses — heating, cooling, heating — with about one-half -hour 
intervals; (8) a final heating for one half -hour to 176°-212° 
F. (80°-100° C); and finally (9) cooling to 59° F. (15° C). 

Good results can doubtless, as a rule, be obtained by 
this or a similar method of procedure. Difficulties of all 



STERILIZATION OF MILK. 155 

kinds have, however, arisen also here. First of all, per- 
fectly satisfactory condensing-cans have not been obtained. 
Those applied by Dahl were of sheet iron, and were made 
air-tight by soldering the cover on. The weak points of 
these cans are, that they can only be used once — when the 
can is once opened the milk will spoil comparatively soon ; 
and they are, rather expensive to be used for so cheap an 
article as milk. Glass bottles would be far better in many 
respects, but they are so easily broken during the heating 
as to greatly increase the expense of the sterilization. 

Like Scherff's method, that of Dahl has been modified 
in many ways without any really practical and reliable 
method for the preservation of the milk having, to my 
knowledge, yet been found. The difficulties which have 
not yet been overcome are partly that the proper preserv- 
ing cans come too dear, partly that the milk is not com- 
pletely sterile, or else must be heated so high that it 
assumes a disagreeable cooked taste, and is changed in 
quality and appearance. Different apparatus have been 
constructed, and preserving-cans of the most varying kinds 
have been invented and improved. [Among German 
methods which have given satisfactory results in practice 
may be mentioned that of Neuhaus, Gronwald, and Oehl- 
mann (see Weigmann, " Milchconservirung," 1893, p. 47). 
In the investigation made by Petri and Massen in regard 
to milk sterilized by this method they found, however, 
among the six hundred bottles examined " a large num- 
ber of bottles" containing living bacteria.*] Patents in 
large numbers have been granted in different countries, 
and each inventor has claimed with confidence that the 
problem has been solved, and that his apparatus and 
method may be successfully applied anywhere. 

The bacteria found in milk during different seasons 
* Author's addition to American translation, 



156 MODERN DAIRY PRACTICE. 

and under different conditions vary so greatly that the 
sterilization of milk on a large scale must always remain 
a difficult problem. In my opinion we ought to begin 
with reforms in the cow-stable, and better milk, contain- 
ing fewer bacteria, than that now generally available, 
should be supplied. Some milk is difficult to sterilize and 
other milk is easily made germ-free. Sometimes this may 
be attained by a single heating of three fourths of an 
hour; sometimes, again, the operation has to be repeated 
for three or four days. According to my investigations 
this depends, without doubt, on the treatment which the 
milk receives on the farm. The milk from the same 
farms also shows a certain regularity as regards the diffi- 
culties met with in its sterilization.* 

As long as the question of the sterilization of the milk 
by heating for practical purposes is at its present stage we 
ought, however, in my opinion, to receive with great re- 
serve claims that some experimenters have succeeded in 
solving the problem. 

[Since the preceding account of the sterilization of 
milk was written (1891), the question has not received any 
further light. An excellent exposition of the subject is 
given by H. Weigmann in his small work, already referred 
to, on " Methods of Preservation of Milk " (" Die Methoden 
der Milchconservirung," Bremen, 1893, 176 pp.), to which 
the reader interested in the subject is referred. The book 
is especially complete as regards descriptions of different 
kinds of apparatus and methods proposed for the steriliza- 
tion and pasteurization of milk.f] 

* The preparation of absolutely germ-free milk is more easily 
accomplished the purer and fresher the milk used, — a fact which 
is of the greatest importance to milk-condensing factories as well as 
to physicians and persons using sterilized or even pasteurized milk. 
See Weigmiinn, " Milchconservirung," 1893, p. 51. — W. 

f Author's addition to American translation. 



CHAPTEE VII. 
PASTEURIZATION OF MILK. 

One phase, and perhaps the most important one in the 
sterilization of milk, has not yet been touched upon, viz., 
that at the same time as the milk has been made to keep 
it has also been improved from a hygienic point of view. 
Milk is an exceptionally good nutritive medium for most 
bacteria; we know that it has been the means, although 
comparatively seldom, of spreading various dangerous 
diseases, as tuberculosis, diphtheria, typhoid and scarlet 
fever. These are all infectious diseases caused by different 
kinds of bacteria. The bacteria thrive well in milk; 
once there and with the person consuming the milk liable 
to contagion, infection and disease will easily be the result. 

The pathogenic bacteria existing in milk are fortu- 
nately all killed rapidly at a comparatively low tempera- 
ture. Special investigations have shown that they can 
hardly stand a heating up to 167°-185° F. (75°-85° C.).* 
It is therefore not necessary to obtain complete sterility 
in the milk to guard against infectious bacteria. 

As regards the other bacteria in milk, I want to call at- 
tention to a point suggested by my heating experiments 
with milk containing bacteria of different kinds. If the 
heating was continued to about 167° F. (75° C.) it was 
shown by subsequent bacteriological examinations that the 

157 



158 MODERN DAIRY PRACTICE. 

lactic-acid bacteria proper had disappeared or else were 
considerably reduced in number, and that even putrefac- 
tive bacteria had decreased in number, although not as 
much as the former. This change in the bacterial content 
was so striking that it could be observed by a mere micro- 
scopic examination, and showed that the pure bacilli forms 
had entirely gained the upper hand after the heating. I 
am not in possession of sufficient medical knowledge to 
state the hygienic importance of the disappearance of the 
lactic-acid bacteria proper from the milk, or at least their 
great diminution, and of the decrease in the number of 
bacteria causing fermentations of the casein; but I can 
testify on the basis of my investigations that this relation 
plays an important part in regard to the keeping qualities 
of the milk, since the lactic-acid fermentation usually 
precedes the fermentation processes caused by the other 
bacteria.f 

The relative keeping qualities of the milk are thus 
increased through the disappearance of the lactic-acid 
bacteria. 

A heating of the milk to 165°-185° F. will therefore 

* Bitter found that tubercle bacilli were killed by simple heating 
for 30 minutes at 154° F. ; Forster {MilchzeiUing, 1894, p. 84) ob- 
tained the same result by heating for 10 minutes at 158° F., for 5 
minutes at 170° F., and for 1 minute at 203° F. At lower tempera- 
tures longer time was required, viz., 1 hour at 140° F. and 4 hours 
at 131° F. Bang found that a temperature of 176°-185° was required 
to kill tubercle bacilli ; see Part IV., Chapter I.— W. 

f Duclaux mentions similar observations in the January number 
of Annates de l' Institute Pasteur for 1891, and ascribes great 
hygienic importance to the fact that the acid-forming bacteria have 
disappeared in the heated milk, especially in regard to the applica- 
tion of the milk for baby-feeding. 



PASTEUKIZATION OF MILK. 159 

not only protect the consumer from infection of con- 
tagious bacteria, but will also appreciably increase the 
keeping quality of the milk. Such heating has been called 
pasteurization, and is now practised at a large number of 
creameries. This treatment of the milk is especially 
necessary at large factories where it is difficult to properly 
supervise cleanliness, etc., at the farms of the patrons. 
The details of pasteurization will be treated farther on in 
this book. 

There are, however, two cases in which still greater 
precautions are necessary for preventing infection from 
milk, namely, at milk sauatoriums and for baby-feeding. 
In both cases large quantities of milk are consumed, and 
if this is infected by malignant bacteria infection may 
easily arise. 

Milk for Sanatoriums. — At milk sanatoriums the effort 
is of course to supply milk from as healthy cows as possi- 
ble and to observe all possible neatness and cleanliness in 
the production and handling of the milk ; besides this an 
obligatory heating of the milk is practised. This is the 
case, e.g., at the milk sanatorium in Berlin under the 
direction of the well-known dairy authority Benno Mar- 
tiny; all milk is there heated for half an hour to about 
176° F. previously to consumption. 

Milk for Baby-feeding. — The milk intended for baby- 
feeding must also undergo a special treatment.* Babies 

*Incaseof milk intended for sanatoriums or for baby-feeding, 
special care must be taken as regards the system of feeding the 
cows. Only well-preserved, carefully-selected feed stuffs should be 
given. Sweet aromatic and well-cured hay or corn fodder is the 
best coarse fodder for the purpose. Corn silage must be fed only in 
small quantities, if at all ; always after milking, and not to exceed 
10-15 lbs. a day. Oat or barley straw may also be fed ; likewise 



160 MODERN DAIRY PRACTICE. 

often consume cows' milk in large quantities, and their 
systems possess less power of resistance than that of grown 
people, f But even here it may not be necessary to strive 
to reach complete sterility, since infectious bacteria do not 
appear to be very resistant toward heating. If precautions 
are taken that the milk is always consumed within twenty- 
four hours at the latest after the heating process, and that 
it is kept in a cool place during this time, it will not be 
infectious or undergo any injurious changes. 

The same results may be obtained by heating the milk 
in an ordinary casserole to the boiling point, or even only 
to about 158° F. It must be remembered, however, that 
such a heating does not of course protect the milk from 

rutabagas or carrots (in small quantities). Of concentrated feed stuffs, 
the cereals or the flour-mill refuse-products may safely be fed, but not 
pea-meal, bean meal, or any other legumes. Malt-sprouts, linseed- 
meal, palm-nut meal, cocoanut-meal, etc., may be fed sparingly — all 
but the first-mentioned not to exceed one pound of each feed a day 
per head. No fermented or rancid feed should be given (except 
silage, with the proviso mentioned), and no slump feed, brewers' 
grains, etc. The milk from fresh cows should not be used for this 
purpose until the eighth day after calving, and never under any con- 
dition unless the cows are perfectly healthy and give milk fully 
normal according to both taste, smell, and appearance. — W. 

fMunkand Uflfelmann (in their "Ernahrungd. Menschen," 1891, 
p. 294) state that " the high germ content of cows' milk, especially 
of fermentative forms, is doubtless largely the cause of its poorer 
utilization and palatability in baby-feeding. Soxhlet considers the 
particles of dung very frequently, present in cows' milk the main 
carriers of these bacteria; and he is doubtless right. Experience 
teaches us at any rate that feeding babies with boiled or especially 
with sterilized milk gives far belter results, and causes a much 
smaller number of digestive troubles, stomach and intestinal catarrhs, 
etc., than does feeding with unboiled milk." — W. 



PASTEURIZATION OF MILK. 161 

renewed infection before it is consumed. To prevent this 
infection, which is a very important point in case of baby- 
feeding, the milk must be heated and kept in a sterile and 
carefully closed vessel. Many different kinds of apparatus 
and methods have been invented for the treatment of milk 
for this purpose. I shall here only mention two methods 
which may be considered typical. The one was invented 
by Dr. Engli-Sinclair in Switzerland; the other by Dr. 
Soxhlet in Germany. Both these methods are essentially 
alike : Engli-Sinclair works with simpler and more primi- 
tive apparatus than Soxhlet. Both methods seem to give 
perfectly reliable results, although the admirers of the 
Soxhlet method maintain that that alone fulfils the de- 
mands for an ideal milk-sterilizing apparatus. 

Methods of " Milk-sterilization." * — The method of 
Engli-Sinclair is as follows : In an ordinary porcelain-lined 
iron casserole provided with a cover a sheet-iron stand is 
placed holding seven bottles; these will hold about 1. 6 liters 
(1| quarts), or about as much milk as is required for one 
meal. The bottles are filled with milk of the best quality, 
which if necessary is diluted with water; the bottles are at 

* There is some confusion in the use of the term sterilization and 
pasteurization of milk and milk products. Sterilization, as we have 
seen, implies absolute freedom from bacteria, while pasteurization 
implies relative freedom from bacteria; the former is reached by 
prolonged heating at the boiling-point or higher temperatures; the 
latter by heating at temperatures from 165°-185° F. (see p. 159). 
When the methods to be described in the above were given to the 
world, it was thought that the product obtained was absolutely germ- 
free, and the process was therefore called sterilization of milk— a name 
still applied, although according to our present knowledge it is not 
strictly correct. The methods are described in the present chapter 
because the milk thus treated will act like pasteurized milk, as will 
be apparent from the remarks of the author. — W, 



162 MODERN DAIRY PRACTICE. 

once, without being stoppered, lowered into the casserole, 
which is filled three fourths full of water. The casserole 
is now put over the fire, and when the water is boiling hard 
the bottles are hermetically sealed with rubber stoppers and 
the cover put on the casserole. After half an hour the cas- 
serole is taken away from the fire and kept in a cool place. 
The bottles must cool in the casserole, as otherwise they are 
liable to break. The same bottles are used for nursing, 
and a nipple carefully cleaned and boiled each time is 
substituted for the cork. In this way the different milk 
portions are comple'tely protected from contamination until 
the very moment they are to be consumed. 

The milk is treated exactly according to the same prin- 
ciples in Soxhlet's method. The superiority of this method 
consists in the fact that the apparatus may be used by any 
one, and is more easily kept clean, which is a very impor- 
tant point.* As fresh milk as possible is to be used, and 
never milk from a single cow — only mixed milk. The dilu- 
tion of the milk with water should always take place before 
the boiling. The milk must be boiled for three quarters of 
an hour. The rubber rings on the bottles should not be re- 
moved until the milk is to be used. The covers should 
also be left on the bottles, and the latter kept in a cool 
place after the boiling. When the milk is to be used it 
should be heated to body temperature. It is to be remem- 
bered that the cold bottles must not be placed in hot 

* Soxhlet's apparatus with the latest improvements can be ob- 
tained from the manufacturer, Metzeler & Co., in Munich, at a price 
of 13 to 16 marks. A collection of the most necessary pieces may be 
obtained from the same firm for 10 marks. The apparatus can doubt- 
less be obtained from American dealers in chemical glassware or 
from wholesale druggists. — W. 



PASTEURIZATION OF MILK. 163 

water; if they do not break immediately in such a case 
they will become brittle and readily break in the next 
boiling. Milk residues in the bottles should not be saved. 
The cleaning of the bottles is best effected as soon as the 
milk has been consumed. 

Ardent adherents of Soxhlet's method claim that milk 
treated in this way will keep for three to four days, and 
advise that large quantities of milk be sterilized at once. 
This is doubtless an exaggeration. One of the best points 
in the method is in my opinion the fact that small quanti- 
ties of milk may be easily and cheaply treated. If such 
incompletely sterilized milk is saved for a longer time than, 
e.g., twenty-four hours, risks are doubtless taken. If living 
bacteria are found in milk they will necessarily soon make 
their presence known if it is kept longer, and not in a 
cool place. 

Milk treated according to Soxhlet's method seldom 
becomes absolutely sterile. I have made numerous ex- 
periments on this point and have kept milk carefully 
prepared in a Soxhlet apparatus at a temperature of 90° F. 
(33° C.) in an incubator; I have practically every time 
within forty- eight hours been able to verify in it a large 
number of Bacillus-siihtilis forms and other bacteria. 
Soxhlet warns against sterilizing such large quantities at 
one time that the milk has to be kept long before being used. 
He holds that lactic acid is almost exclusively formed in 
unboiled milk kept at 95" F. (35° C); butyric acid formed 
at the same time does not make up even 4 per cent of the 
total acidity. Large quantities of butyric acid are, on the 
other hand, formed in samples of partially sterilized milk — 
at least 15 per cent, on an average 30 per cent, and often 
more than 50 per cent of the total acidity. This butyric 



164 MODERlf DAIRY PRACTICE. 

acid must be considered injurious, and it seems therefore 
safest to prepare only as much milk as will be used during 
twelve hours. Soxhlet has also constructed an arrange- 
ment for heating milk up to the proper temperature imme- 
diately before consumption. 

In many larger cities, as, e.g., in Vienna (Dr. Hoch- 
singer), so-called milk-sterilizing stations have been estab- 
lished, where children's milk is prepared on a large scale 
according to Soxhlet's method and is sold in definite mixt- 
ures of milk and water according to the prescription of 
jihysicians. If careful supervision is given to the station, 
so that everything is conducted as it ought to be, this is an 
excellent idea, since pasteurized milk in this way can be 
had cheaper than if everybody pasteurize milk for their 
own use. The Soxhlet apparatus is rather expensive, 
and the cost is farther increased by the frequent breakage 
of bottles. The cleaning of the apparatus demands time 
and care. Engli-Sinclair's method is cheaper, as before 
mentioned, but may require greater care in execution than 
that of Soxhlet. 

The methods just explained have gained still more in 
importance since it has been proved that the indigestible 
condition of cow's milk does not really arise from its chen;- 
ical composition, but from its " unavoidable contamination 
with micro-organisms " which in some way or other cause 
disturbances in the digestive organs of nursing children.* 

I must finally mention that although pasteurization 
will kill the majority of bacteria, the danger that the milk 
may occasion sickness is not in all cases entirely removed. 
Some bacteria are found producing poisonous principles by 

* See foot-note on p. 160. 



PASTEURIZATION OF MILK. 165 

their living actions, which are not destroyed by the heat 
applied.* 

Fortunately these substances appear very rarely in milk, 
and seem to originate from bacteria thriving best in dark, 
filthy, and poorly-ventilated places. Sterilization of the 
milk does not, therefore, render it unnecessary to observe as 
great cleanliness and care as possible in the production and 
handling of the milk. 

* As an example it may be mentioned that a poisonous principle 
{tyrotoxicon) is sometimes found in milk (see " Hygiaea," 1888, p. 695). 
In the case quoted it had arisen after the milking, in milk kept in a 
building with poor ventilation, the grounds of which were exposed 
to contamination from a neighboring slaughter-house. The milk 
caused a cholera-morbus-like disease in children. Boiling or sterili- 
zation did not diminish the injurious effects of the milk. See also 
Flugge, "On Sterilization of Milk," Zeitschr.f. Hyg., 17 (1894), pp. 
272-342. 



PART 11. 

CREAM. 



CHAPTER I. 
CREAM RAISED BY GRAVITY PROCESSES. 

a. The Old Shallow Setting System. — In the old 

shallow setting system of cream separation the cream is 
allowed to sour on the milk. This method is still com- 
mon in our country at the present, the greater portion of 
our farm butter being made from cream raised in this 
way. As the method is practised on most farms it is not 
attractive ; a good many of the faults to be found with it 
do not, however, really belong to the method itself, but 
are coincident with it. The farmer's wife has generally 
to fight the worst conditions imaginable in her dairy, es- 
pecially in winter-time. During this season the milk is, 
first of all, of the poorest quality, on account of the scant 
feeding. It is furthermore usually milked in dark stables, 
where the cows are standing on manure, with no good litter 
under them. It is natural that the milk under these con- 
ditions should come in intimate contact with dung par- 

166 



CREAM RAISED BY GRAVITY PROCESSES. 167 

tides and other filth. The milk-pail also shows variegated 
colors, testifying to slovenliness; and as it is often used 
for feeding meal and milk to the calves, it is natural 
that it never dries out thoroughly. The pail harbors 
luxuriant bacteria and mold-cultures, as any one can 
satisfy himself if he places such a pail in a clean room, 
where the air is fresh : it will not be long before colonies 
visible to the naked eye may be seen, especially if the wood 
is kept moist. 

Milk subjected to such conditions cannot possibly 
keep well. If an effort is made to prepare palatable, well- 
keeping cream by this method by means of ice, in nine 
cases out of ten we shall not succeed. 

The conditions in the dairy, if such a building or room 
be kept, are also such as to prohibit the production of 
first-class cream. It is often dark, dirty, and poorly ven- 
tilated,. and frequently also used for other purposes. The 
milk is therefore exposed to the most unfavorable con- 
ditions during the winter months, and as a result good 
butter cannot be produced during this time. 

During the summer season matters are fortunately dif- 
ferent. The quality of the milk is then of the very best, 
thanks to our good natural pastures. The cows are 
milked in the open air, although often in muddy inclos- 
ures. The udder and hind-quarters of the cows are fairly 
clean, as the animals often have a chance to stand in some 
lake or stream, and as they never soil in the pasture as in 
the stable. The milk-pail also has a better appearance, 
being thoroughly aired in light and sunshine. The con- 
dition of the milk-pans is also very different in summer- 
time. They are not only well scrubbed, but are often 
placed outside in the sunshine with the churn and other 



168 MODEEN DAIRY PRACTICE. 

household utensils. This is in my opinion the great 
secret and the main reason why farm butter can be first- 
class and of good keeping quality during the summer-time, 
in spite of many unfavorable conditions and poor facili- 
ties. As previously shown sun rays in a short time kill 
all bacteria. The putrefactive butyric acid and similar 
darkness-loving bacteria seem to be easily destroyed by 
direct sunlight. The lactic-acid bacteria are also sensitive 
to their action, but according to my experiments are not 
so easily killed in sunlight as the former. The presence of 
lactic-acid bacteria in the milk-pans is not, however, as 
injurious for the milk as that of putrefactive and butyric- 
acid bacteria — a point which will soon be further ex- 
plained. 

The conditions to which milk is subjected during 
the separation of the cream are also far more favorable in 
summer-time. The air in the dairy is better; the small 
window usually found is insignificant, but it constantly 
acts as a ventilator, being usually left open; the door is 
also left open a large share of the day, so that a draft 
is created. Outside the door of the dairy there is usually 
a lawn, and dust or dirt from the surrounding regions 
are not therefore very apt to be brought in from the 
outside. 

Having now considered the conditions present where 
the old shallow setting system of cream separation is prac- 
tised, we shall consider in how far the unfavorable con- 
ditions for the keeping quality of the products are de- 
pendent on the method itself. 

For one thing, uncleanliness does not at all belong to 
the method. The lack of neatness often found among 
farmers using the system comes from their poverty and 



CKEAM RAISED BY GRAVITY PROCESSES. 169 

lack of knowledge. Give the farmer more education and 
knowledge and better conditions of life, and it will not be 
long before the quality of the milk and the whole dairy 
business on the farms will be revolutionized. 

The straining of milk into wooden dishes is also ap- 
plied in the Holstein method, which is still used in many 
places abroad. It has been proved beyond a doubt that 
first-class aromatic products of good keeping quality may 
be obtained by handling the milk in wooden vessels. 
These require greater care in cleaning, and are therefore 
not adapted to creamery use, but they have advantages 
which tin vessels lack. As is well known, wood is a poor 
conductor of heat, for which reason wooden dishes are very 
suitable to the simple conditions present in the dairies of 
ordinary farms. No special arrangements are necessary to 
keep the milk in them at something like an even tempera- 
ture, and comparatively much and good cream is obtained 
by their use. 

The milk is allowed to sour spontaneously in this 
method, but up to very late there was no rational and 
systematically conducted ripening, even in the most modern 
dairy methods — a lack which certainly has not been 
to the advantage of the products. The modern dairy 
practices need to be reformed in this respect as well as 
the old-fashioned method here considered. Even the latter 
is not incompatible with such a systematic souring, as we 
shall see later on in this book, where more detailed 
directions for this souring will be given. 

In this system of cream separation the ripening takes 
place at the same time as the cream -raising. By closer 
examination this is found to possess both advantages and 
disadvantages. 



170 MODERN DAIRY PRACTICE. 

If we compare this method with, e.g., the Holstein 
method, we find that the cream-raising and ripening in 
the latter demand a very long time, because the milk is 
creamed under conditions which do not hasten this pro- 
cess and the cream is not ripened until after skimming. 
In the old shallow setting method these processes go hand 
in hand, and under favorable conditions occur more 
rapidly than in the method just mentioned, especially if 
we consider that the pans used by the farmer hold more 
milk than the Holstein pans — which is a decided advan- 
tage. This method cannot of course be compared with 
the centrifugal method as far as rapidity in reaching 
the result goes; but, as my experiments have shown, we 
can obtain a properly soured cream in a good deal shorter 
time by this method than is required by the ice method if 
the milk-room is kept moderately warm and a good 
starter is added to the milk. 

It is often stated that a smaller quantity of butter is 
obtained by the old shallow setting method than in the 
modern methods of cream-raising. Eepeated direct ex- 
periments conducted by me do not bear out this assertion, 
however. I shall here briefly report an experiment made 
last summer. 

The same quantity of the same milk was treated ac- 
cording to the separator, the ice, and the shallow setting 
system, care being taken in all cases to observe the di- 
rections for the different methods with the greatest possi- 
ble accuracy. The milk was separated at 86° ¥., the 
separator (de Laval) making 7600 revolutions per minute; 
the separated cream was ripened in the usual way in 
eighteen hours. In the ice method the milk was left for 
twenty-eight hours, the temperature of the room being 



CREAM RAISED BY GRAVITY PROCESSES. 



in 



54° F., and that of the water in the creamer 36°. The 
cream was ripened in the same way as in the separator 
method. In the shallow setting method the milk was 
strained into wooden pans holding about three quarts. It 
was left for forty-eight hours in a room with a tempera- 
ture of 54°, to allow the cream to raise and the souring to 
take place. It was then removed to another room with a 
temperature of 64° F., where it was kept for twelve hours. 
When the milk was skimmed the casein was evenly coagu- 
lated. The experiment gave the following results: 





MUk. 


Temper- 
ature— 


Products. 


Hours 

re- 
quired 

for 
Cream- 
rais- 
ing. 


Hours 

re- 
quired 

for 
Ripen- 
ing. 


System of Crflam-raising. 


of 
Room. 


of 
Milk. 


Cream. 


Butter. 


Separator method 

Ice method 


Lbs. 
125.4 
125.4 

125.4 


op 

64 

54 

54^64 


op 

86 
36 

59 


Lbs. 
26.6 
23.8 

17.8 


Lbs. 
6.4 
5.5 

5.5 


'28' 


18 
18 






Shallow setting method 


60 



As might have been predicted, the yield was largest in 
the separator method, but similar quantities of butter 
were obtained in the two other methods from the same 
quantity of milk.* 



* Without doubting the correctness of the figures given in the 
foregoing experiment, I cannot agree with the author that the old 
method of cream-raising will in general give as good results, as far 
as yield of butter goes, as do the modern methods. The per-cent of 
fat left in the skim-milk obtained by the various processes will, as 
it seems, show that such cannot be the case. Skim-mllk from 
shallow pans set in the air in my experience always contain over 
1 per cent of fat, often over 1.50 per cent; while deep-setting skim- 
milk cooled by water will contain from .50 to 1 per cent of fat, 



172 MODERN DAIRY PRACTICE. 

The main objection to this method is that the skim- 
milk sours at the same time as the cream. This is a seri- 
ous objection from one point of view, but many farmers 
accustomed to the wholesome and refreshing sour milk 
obtained in the old method often complain that they 
cannot get as good, delicious sour milk when this is made 
from sweet skim-milk. It is doubtless a fact that the 
two kinds of sour milk taste entirely different. It is also 
natural that such should be the case, for in one instance 
the milk is allowed to sour slowly in a relatively shallow 
layer, while in the other it sours rapidly in deep ripening 
cans. I have also found that the layer of cream on the 
milk in the shallow pans has a special influence on the 
acidity and taste of the underlying skim-milk, evidently 
because this condition favors the growth and develop- 
ment of special bacteria. 

A weak point in this method is the fact that the skim- 
milk can only be boiled with difl&culty. Farmers prefera- 
bly use their skim-milk as sour milk, however, and only 
rarely consume boiled milk, so that this point is not very 
important. Another question on which I dare not express 
an opinion is, whether it would be right from a hygienic 
point of view to agitate against the abundant coLSumption 
of sour milk by the people. In passing I will add that 

aud cooled by ice from .20 to .50 per cent of fat. Fleischmann 
gives the following number of pounds of milk as required for 
making one pound of butter : creaming in high pans at 15° C, 
33 lbs.; in shallow pans at 15° C, 31 lbs.; in the Gussander method 
(see second division of the present chapter), 29.5 lbs.; in cold- 
water setting, the Holstein method, and Schwartz's method, 29 lbs. 
of milk. The results of Fjord's experiments (17th Dairy Report, 
1882) go in the same direction. — W. 



CBEAM RAISED BY GEAVITY PROCESSES. 173 

a large number of infectious bacteria do not thrive in a 
substratum containing large quantities of lactic acid. 

Bacteria m Shallow-setting Cream. — Proceeding to a 
statement of the bacteria which my analyses of cream pre- 
pared according to the shallow-setting method have shown 
present, we first note that this cream when left on the 
skim-milk shows a downy surface, especially when near the 
ripening stage. This down comes from a growth of the 
milk-molds {Oidium lactis) spoken of before. The part 
which the molds play may be manifold : by their alkaline 
reaction they may be the cause of the lactic-acid bac- 
teria thriving and living for a somewhat longer time in 
the sour cream. These molds also consume the acid in 
the upper layer of the cream, thus causing a weakening of 
acid in the lower layers of the milk, through which these 
become better adapted to the anaerobic bacteria. Investi- 
gations made after the first part of the original of this 
work was written show that if we want to study the 
anaerobic bacteria of the milk we may conveniently seek 
them in just such milk-pans overgrown with molds. 

Those milk fungi furthermore appear to protect the 
milk from later and possibly more dangerous infection. 
They grow fast and spread, especially in the upper layers; 
and if they were not there, more dangerous micro-organ- 
isms would most likely take their place. 

Excepting the molds mentioned, I have not, in spite of 
numerous bacteriological analyses, been able to discover 
any micro-organisms characteristic of this cream. The 
bacteria -found, both those infecting the milk as well as 
the useful and desirable lactic-acid bacteria, are mainly 
the same as those found in any other cream allowed to 
sour spontaneously. A couple of points are, however, 



174 MODEEN DAIRY PRACTICE. 

to be observed in this connection. Bacterial infections 
are first of all, as a rule, more numerous in cream which 
has soured on the milk than in that prepared according 
to modern methods. Their number will vary greatly. In 
examining cream from the same milk obtained by the dif- 
ferent methods the shallow-setting cream has usually 
been found richest in bacteria not producing lactic acid, 
although this was by no means always the case. A very 
small number of such bacteria were found in the cream if 
the milk had been strongly infected with lactic- acid bac- 
teria. The quality of the cream was then as good, from a 
bacteriological point of view, as if it had been prepared 
according to the ice method, and often better. The ex- 
planation is doubtless to be found in the fact that the 
early-appearing mass-infection (see p. 93) of lactic-acid 
bacteria hindered the growth of other bacteria. In this 
way the ripening took place rapidly and at the same time 
as the raising of the cream, so that if the infection took 
place at the proper time the cream was sufficiently sour 
and coagulated just at the end of the separation. 

Another point to be noticed is that yeast-fungi taking 
part in the starting of the lactic-acid fermentation have 
been found only in the cream and sour milk from small 
farm-dairies. I have found such yeasts in " stringy " milk 
from Borgaa and in buttermilk from Savolaks and 
Karelen. 

Very different kinds of lactic-acid bacteria may appear 
at the same time in the sour milk and cream on neighbor- 
ing farms. A fact which will be further considered when 
the question of cream-ripening comes up is that in some 
farm-dairies I have met with buttermilk containing prac- 
tically only lactic-acid bacteria. These samples of butter- 



CREAM RAISED BY GRAVITY PROCESSES. 175 

milk originated on particularly well-conducted farms, 
where tlie housewife herself took care of the milk. By 
accident I learned of one of these farms that it had the 
reputation of making first-class, well-keeping butter. A 
separation and ripening of the cream according to this 
method can therefore be well conducted and give good 
results. 

Having studied the conditions oi this method of cream- 
raising, and learned how bacteria generally appear in the 
cream, we shall briefly consider its keeping quality. From 
the point alone Just mentioned, that such cream is gener- 
ally mixed with a great number of non-lactic-acid-produc- 
ing bacteria, we may conclude that usually it will not 
keep long; but we have seen that under favorable condi- 
tions cream may also be obtained by this method which 
will contain practically pure cultures of lactic-acid bac- 
teria. How this exceptional condition may become the 
rule, or at least more general, will be shown in a later 
chapter. From the description given it will be seen that 
it has its good points, and that the method hardly deserves 
the scorn shown it by writers and speakers on dairy topics. 

h. The Modern Systems of Gravity Creaming. — In the 
more modern creaming methods neither cream nor skim- 
milk undergoes any appreciable change during the cream- 
ing. The principle both in these methods (the Holstein, 
Gussander, Swartz, and Cooley methods), as well as in the 
separator and extractor methods, to be considered in the 
next chapter, is, that the fermentation bacteria are not al- 
lowed to develop to any appreciable extent, either before 
or during the rising and separation of the cream. 

Two objects have constantly been kept in view in the 
older of these methods : to favor the rising of the cream , 



176 MODERN DAIRY PRACTICE. 

and as far as possible to prevent the fermentation bacteria 
from developing their specific functions. We shall here 
dwell mainly on the latter object. 

As we have seen, the milk always contains a larger or 
smaller number of bacteria when set. According to my 
experiments the number of bacteria in cream from 
Swartz's cans may vary from less than 100 to several tens 
of thousands per cubic centimeter — the conditions of 
creaming being the same in all cases. The variation de- 
pended entirely on the handling of the milk before setting. 
If the milk has been handled with the greatest cleanliness 
and accorJii]g to the princijiles previously dwelt on, the 
number of bacteria in the cream will not only be smaller, 
but the bacteria found will not as a rule be of such unde- 
sirable forms as will otherwise be the case. 

The means at hand for the checking of the fermenta- 
tion bacteria during cream-raising are, of course, the same 
as stand at our disposal in the keeping of the milk, viz. : 

1. Scrupulous cleanliness throughout the dairy, es- 
pecially as regards the creaming-vessels, etc. 2. Cooling 
the milk as quickly as possible; and, 3. Light, fresh, and 
dry creaming-rooms. 

The lactic-acid organisms are generally best fought by 
the first two methods, but the last method also tends to 
check them, though not to the extent in which it checks 
putrefactive and similar bacteria. 

The oldest method of creaming of this kind is the 
Holstein system. In this method the complete rising of 
the cream is secured by the thinness of the layer of milk 
and by a rather high temperature, at which the milk-serum 
is but little viscous. The development of the bacteria 
is rather incompletely checked. The temperature sinks 



CEEAM RAISED BY GRAVITY PROCESSES. 177 

slowly in the j)ans, and the final temperature (55°-59° F.), 
while not very favorable to the bacteria, is yet by no means 
unfavorable; and as the milk is under the influence of this 
and still higher temperature for at least thirty-six hours, 
it is evident that a considerable bacterial growth will take 
place. It is also often very difficult in this method to 
fight especially the lactic-acid bacteria, and older writers 
on dairy matters, as Martens, dwell at length on the diffi- 
culty of keeping the milk and the cream sweet when this 
method is followed. The difficulty of keeping the wooden 
pans clean is another objection to the method. Martens 
also maintains as the first duty of the dairywoman " to 
have especial attention directed toward the cleaning of 
the dairy utensils. She should always be present at the 
cleaning of the milk-pans and 'personally examine every 
pan." 

In spite of these disadvantages, the method when 
properly conducted gives excellent, well-keei3ing butter. 
The explanation doubtless is found in the minute cleanli- 
ness and dryness (see p. 112) which must be observed where 
it is used. 

In the Gussander method, invented in the '40's by 
Major Gussander in Sweden, the milk is strained in still 
thinner layers than in the preceding method, and the tem- 
perature is generally higher. The rising of the cream is 
facilitated by the short distance to the surface and by the 
lower viscosity of the medium through which it has to pass. 
The milk is here not kept in cellars, as in the Holstein 
method, where a certain moisture of the atmosphere is 
likely to be retained, but in light, cheerful rooms, where 
scrupulous cleanliness is observed, and where fresh, dry air 
can all the time be maintained. Cleanliness was also fa- 



178 MODERN DAIRY PRACTICE. 

cilitated by introducing metal vessels in the creaming of 
the milk. 

The weak point in this otherwise attractive method is 
evidently the high temperature in the milk-room, for which 
reason the milk also, according to numerous testimonies, 
was very apt to sour. It is natural that the lactic-acid 
bacteria under such conditions would get the upper hand 
of other milk bacteria. Putrefactive and similar bacteria 
had very poor chances of life in a Gussander milk-room. 

In the ice method, now generally used in our dairies, 
light and cleanliness are the main weapons for fighting 
the fermentation. But the bacteria are further checked in 
this method by cooling the milk. As before stated, the 
low temperature checks the growth and development of 
the bacteria, but it does hot kill them. If the cooling is 
neglected or conducted so slowly that the bacteria present 
in the milk or in unclean vessels are allowed to develop 
and multiply before the temperature is low enough to stop 
these processes, injurious changes in the milk or its prod- 
ucts may sooner or later be observed. If the cream does 
not become appreciably sour or of an undesirable flavor by 
such manner of procedure, it will still be found that the 
butter made from the cream is not of the good quality it 
would otherwise have been. 

From the results obtained in the laboratory at Eiitti 
(p. 88) we find how immensely quicker and stronger the 
development of bacteria will take place in milk of 77° F. 
than in milk 18° lower. If still lower temperatures had 
been applied it would have been found, as in oiy experi- 
ments (p. 89), that the development decreased more rapidly 
the further the milk was cooled down, and that it stopped 
entirely at 39° F. (4° 0.). 



CREAM RAISED BY GRAVITY PROCESSES. 179 

In the ic< method the milk is creamed in high, usually 
narrow tin cans. These cans are easily cleaned and 
steamed, and it is therefore not difficult to keep them 
sterile. 

Without entering into a general discussion of the ad- 
vantages of this method in our creameries and dairies, I 
desire to call attention to some points about it, the neg- 
lect of which will largely influence the keeping quality of 
the products. 

First of all, I will recall what was said on pp. 62-66 
concerning the necessity of the rapid cooling of the milk 
by the use of sufficient quantities of ice. It is necessary 
not only to use ice liberally, but to use it in the right way. 
It is therefore advisable to have finely-divided ice in the 
creamer instead of large pieces, especially in the first cool- 
ing of the milk, as the fine ice causes a more rapid cool- 
ing of water and milk. When a sufficient decrease in-the 
temperature of the milk has been obtained, larger pieces 
of ice may be used. A mistake often made is to place the 
milk-cans very near one another, not allowing a sufficient 
quantity of ice between them for the rapid cooling of the 
milk. It may furthermore be well to remember that pure 
water must be kept in the creamer. In many creameries 
the same water is left in the tanks for weeks, although 
milk is often spilled into them, thus improving the water as 
a nutritive medium for bacteria. The water is, of course, 
kept cold by the ice floating in it, and the bacteria are 
thus prevented from increasing perceptibly; but water 
often splashes into the milk from the creamer or is spilled 
on the floor and walls, where it evaporates. The bacteria 
coming from the evaporated water may then float in the 
air, and thus easily infect the milk, 



180 MODERN DAIRY PRACTICE. 

Cream obtained by the ice method contains compara- 
tively few bacteria, except in cases where the milk before 
setting was highly infected, or where sufficient cooling was 
not practised. We seldom find molds in it and never 
o'idium fungi, as in case of cream obtained by the shallow- 
setting system. At the temperature used in the ice 
method the molds can evidently not develop in the cream 
layer and form long, threadlike conidia, giving the cream 
a " velvety " appearance. 

This system of cream -raising has an immense advan- 
tage over those previously described as regards the ease of 
combating the fermentation germs by the cooling process. 
If this is properly conducted, bacterial growth may be 
practically stopped, and no fermentations will set up. 
There is always a danger in this respect, however, as is 
plain from the fact that some milk bacteria will reproduce 
at a temperature of 50° F. (10° C). Care must therefore 
be exercised in using the method if first-class results are 
wanted. But if the directions given are carefully followed 
and the milk on hand has not already been overloaded 
with bacteria, we may feel assured that the keeping 
quality of the products will not be diminished during the 
cream separation — a result which cannot be reached in any 
of the other methods so far described. 



CHAPTER II. 
SEPARATOR CREAM. 

The centrifugal method rests on an entirely different 
principle from those previously considered. The heavier 
parts of the milk, the skim-milk, are whirled against 
the circumference of a rapidly-rotating steel bowl, while 
its lighter parts, the cream, remain nearer the centre. 
The result is that not only is the cream separated from 
the skim-milk, but all filthiness present in the milk is 
also forced to the wall, where it forms a tough, sticky 
layer, cailed " separator slime." The separation takes 
place in the manner mentioned, both in the cream sepa- 
rator and the extractor. 

By application of the separator method the cream may 
be separated from the milk as soon as this comes to the 
creamery. The time of infection is greatly shortened, the 
chances of contamination of bacteria decreased, and the 
bacteria already found in the milk do not get time to 
develop. For these reasons this method possesses a de- 
cided advantage over all other methods of cream separa- 
tion known. 

At a large number of separator creameries in this and 
other countries this point is not taken advantage of, how- 
ever, as we often find that the milk, which is usually 
warm when it comes to the creamery, is left for hours in 
the hauling-cans, whereby of course its bacteria have an 

181 



183 MODERN DAIRY PRACTICE. 

excellent chance to increase and start their characteristic 
fermentations. In many places this is done from igno- 
rance; in other places because the number or capacity of 
the separators do not correspond to the quantity of milk 
received. If the danger involved in such treatment of the 
milk was properly understood, the expense of buying a 
sufficient number of separators, or separators of sufficient 
capacity, would not be considered. 

We saw on page 68 the advantage of pasteurizing the 
unskimmed milk to be hauled away, so as to increase its 
keeping quality. Pasteurization of milk is also often prac- 
tised for another purpose — viz., to obtain butter that will 
keep better. It is both expensive and a waste of time to 
separate the cream from such pasteurized milk by means of 
any of the older methods, while it may easily be done by 
application of the centrifugal method. Pasteurization of 
the milk before separation not only gives a product that 
will keep better, but also brings about another advantage, 
as shown by Borje Norling: the production of a thinner 
skimmed milk — i.e., the cream is richer in fat. This 
writer advises that new milk be first pasteurized, then 
separated at about 159° F., the cream and the skimmed 
milk to be cooled in separate coolers. He states that 
numerous comparative trials have shown that if milk 
is skimmed under similar conditions partly at common, 
partly at pasteurization temperature, the skim-milk will 
regularly show a lower fat content in the latter case.* 
The method of pasteurizing the new milk before the 

* Lunde found in his pasteurization experiments the following 
average percentages of fat in the skim-milk, the speed and amount 
of milk run through the separator being the same in both cases : 
skim-milk from pasteurized milk, .14 per cent; from non-pasteurized 



SEPARATOR CREAM. 183 

separation has proved less advantageous in my experi- 
ments, because the cream to a great extent transmitted 
the cooked taste to the butter. This was not the case 
when only the cream was pasteurized, although the temper- 
ature was the same in both cases. The difference doubtless 
came from the fact that a quicker cooling could be applied 
in the latter case. As I consider the presence of a cooked 
taste in butter a very serious fault, I cannot recommend 
pasteurizing milk intended for butter production, and shall 
not therefore here enter into the details of the process. 

Distribution of Bacteria in the Centrifugal Process. 

The centrifugal method has still another advantage 
over the old methods of cream separation, — an advantage 
of which is thought too little, viz., the ability to remove a 
large number of bacteria in the milk, so that the separated 
cream and skim-milk do not (as in the most favorable in- 
stances in the older methods) contain the number of bac- 
teria which were found before the cream was separated 
from the milk, but contain even a smaller number than 
before separation. I have verified in numerous trials that 
a large number of the bacteria present in the milk treated 
were removed from the cream and the skim-milk by the 
centrifugal force and went into the separator slime. This 
can be ascertained by comparing the number of bacteria 
found in the milk before the separation with the number 
found in the cream, skimmed milk, and separator slime 
after the separation. I have made numerous examinations 
of this kind, experimenting with milk poor in bacteria 

milk, .33 per cent fat — the former analyses ranging from .11 to .17 
per cent and the latter from .18 to .3o per cent. — W. 



184 



MODERN" DAIRY PRACTICE. 



as well as with samples containing an immense number 
of them. The following table shows the results of some of 
these investigations: 



Origin of Milk. 



Mixed evening and morning 

milk 

Morning milk 



Number of Bacteria per Cubic Centimeter. 



In New 
Milk. 



18,180 
6,500 
4,100 
1,890 
1,530 
1,640 
1,030 



In Skim- 
milk. 



11,025 
2,025 
3,300 
680 
650 
360 
220 



In Cream. 



13,200 
3,800 
2,480 
550 
480 
450 
200 



In Separator 
Slime. 



4,241,000 
1,320,000 
836,000 
560,600 
650,000 
150,800 
230,000 



It is very peculiar that the cream in most of the above 
experiments contained a larger number of bacteria than 
the skim-milk. I cannot explain this phenomenon. It is 
apparent, however, that even the cream has been appreci- 
ably freed from bacteria and thus improved in keeping 
quality. The immense number of micro-organisms in the 
slime gives also evident proof thereof.* 

* Weigmann {Ldw. JaJirb., Erg-Band I, /. 57; Molkerei-Zeituug 
8 (1894), p. 371) and Scheurlen {Arb. Kais. Oes. Amies 7 (1891), p. 
269/ Filhling's ldw. Zeitung, 1893, p. 575 ; Zeitschr. f. Nahrungsm. 
Uniers., 1893, p. 3) found that by far the greater portion of the 
bacteria goes into the cream by the centrifuging, and only a minute 
quantity goes into the slime. Wyss {Tagb. d. 62. Versarfi. Deut. 
Naturf., 1890; Centralbl. f. Bad., VI. p. 587) found seven times as 
many bacteria in the slime as in the centrifuged milk, and Grernhardt 
(Inaug. Dissert. Univ. Jurjew, 1893, p. 76) found three to four times 
as many. It is possible that the point mentioned by the author in 
the following paragraph (see above) — the varying bacteria content 
of the milk — accounts for the difference in the results obtained by 
the different investigators. — W. 



SEPARATOR CREAM. 185 

Another observation made in this investigation which 
is also shown in the above table is that the fewer bacteria 
the milk contains the more completely has the separation 
purified the cream and the skim-milk. We are here again 
cautioned to observe greater care and cleanliness throughout 
the handling of the milk. The cleaner the milk we start 
with, the greater are the advantages offered by the facili- 
ties in the dairy for keeping the milk good, and the 
better keeping products we obtain; while, on the other 
hand, as has often been stated, slovenliness in the handling 
of the milk during the early stages stamps its mark even 
on the subsequent manufacturing processes and renders 
them much more difficult. 

The greater portion of the separator slime is made up 
of the microscopic filthiness deposited on the inside of the 
separator bowl as a sticky mass,* the quantity of which 
varies according to the treatment of the milk. In my in- 
vestigations this sticky layer has amounted to not less 
than .1 to .3 per cent of the weight of the new milk.f 
This large quantity of filth will remain in the cream and 
the skim-milk in using any of the methods of cream sepa- 
ration mentioned above — a point too little considered, in 
which the centrif uga »method has a decided advantage over 
its predecessors. This point alone is in my opinion so im- 
portant and valuable that it might speak for the universal 
adoption of the separator method. 

It must be observed, however, that the separators can- 

* See further " Afbildningar af komjolk," etc., p. 12. 

f Fleischmauu {Jahresb. Agr. Chemie, 1885, p. 619) obtained 
from .04 to .13 per cent of slime, and Scheuerlen [Zeitschr. f. 
Nahrungsm. Unters., 1893, p. 3) about .04 per cent (130 grams from 
300 liters of milk).— W. 



186 MODERN DAIRY PRACTICE. 

not retain a too thick layer of slime in the bowl, and if 
much filth is accumulated on it, part of it will again be 
washed off and will mix in the cream and the skim-milk. 
To prevent this new infection we must avoid running the 
separators many hours without interruption, and special 
attention must be given to their cleaning. AVhen con- 
ducted in the right way the separation will, however, im- 
prove the milk, decrease its bacterial content, clean it and 
make it keep better. 

The results of my investigations thus differ from those 
obtained by Professor Ejord in Denmark in his investiga- 
tions of separator skim-milk, where he found that centri- 
fuging the milk neither injures nor improves its keeping 
quality. He doubtless worked with highly -infected milk 
containing large quantities of bacteria even after the 
separation, and these soon made their influence felt at the 
high temperature applied. 

The nature of the different bacteria may also be of some 
importance in regard to this question. In making similar 
boiling experiments of separator skim-milk as conducted by 
Fjord in the investigation mentioned, I have as a rule been 
able to prove a very high keeping-quality in the separator 
milk. Exceptions always occurred in cases where the milk 
was very rich in bacteria before the separation. 

[Scheuerlen has also shown that even strong separation 
only partially purifies a highly infected milk from bacteria, 
and different kinds of bacteria behave differently under the 
influence of centrifugal force. He calls special attention to 
the fact that tubercle bacilli and some lactic-acid bacteria 
are easily separated into the slime in separation, while, e.g., 
the typhus bacillum is usually found in the cream.*] 
* Author's addiliou lo Ameriaiu trauslation. 



SEPARATOR CREAM. 187 

In his investigations of tuberculous milk Bang did not 
succeed in purifying it entirely from bacilli by means 
of the centrifuge. I also have been unable to remove all 
bacteria from milk infected with the ordinary milk bac- 
teria by means of separation. If we cannot obtain milk 
free from bacteria by the use of centrifugal force as ap- 
plied in our ordinary separators, it does not follow that 
the decrease in the bacterial content of the milk before 
spoken of is of little importance. In case of infectious 
bacteria, as in Bang's investigations, the results proved 
on the whole of small account, as milk but slightly 
tuberculous must be considered injurious to health. But 
the matter is quite different in case of fermentation bac- 
teria: the fact alone that their number is decreased by 
the separation makes this method decidedly better than 
all other methods of cream-separation now known. 

The cream having been freed from a large number of 
its bacteria in the separator process, we must see to it that 
the advantage gained is not lost through bad treatment. 
The danger is here great from the beginning, as the tem- 
perature of the newly-separated cream is very favorable to 
the development of the bacteria, the temperature of the 
milk when separated being usually about 86° F. (30° C). 
We cannot therefore be surprised that the cream will soon 
be filled with a large number of bacteria if its temperature 
is not rapidly lowered. 

As both the cream and the skim-milk come from the 
separator in thin streams they offer a large surface of in- 
fection, and it is therefore absolutely necessary not to 
allow dirty or dusty persons to approach the separator; 
this is, however, permitted to pass unnoticed in many of 
our creameries. The air in the separator-room must for 



188 MODERN" DAIRY PRACTICE. 

tlie same reason be kept pure and fresh; the cream-can 
must, of course, be as clean as possible, and preferably 
recently sterilized by steaming. 

But these precautions alone will not suffice. We must 
also take measures to act directly on the bacteria found in 
the newly-separated cream, and check their growth. The 
measures applicable for this purpose are well known from 
the preceding. One is the rapid cooling of the cream to 
a temperature at which bacteria do not develop, and the 
other is pasteurization and subsequent rapid cooling of the 
cream . 

Both these methods of preserving the cream are at the 
present too seldom applied in our creameries; there is no 
doubt that great harm is done by the neglect of these 
precautions, for we may easily, at this point in handling 
the milk products, lose all that has been gained by pre- 
vious care and neatness in stable and dairy, and by the 
separation. 

Cooling the Cream. — The advantage in cooling the 
cream need not here be further dwelt upon : cream acts 
in this way just as milk does, so that what was said con- 
cerning its cooling is true also in case of cream. 

When the separator method was introduced in the 
creameries it was believed that cooling would not be neces- 
sary immediately after the separation, and it was expected 
that less ice would be needed in the creamery as a result. 
Experience soon proved this to be erroneous, however. 
The products would not keep well, and were not first-class. 
Then the cream and skim-milk were cooled, and the 
quality of the products was immediately improved. It is 
now considered a maxim that the cream must be cooled as 
soon as it comes from the separator. 



SEPARATOR CREAM. 189 

We must not imitate foreign creamery-men in this 
respect, for they greatly neglect the proper cooling of the 
cream; the reason of this is not that they are blind to the 
importance of the cooling process, but they have only limited 
means of cooling. It is not sufficient to lower the tem- 
perature of the cream to 50°-54° F., as is done in many 
places. The consistency of the butter is fairly good 
even with such a cooling of the cream, but the keeping 
quality is often not what it ought to be. A full step must 
be taken, and the temperature lowered below 50° F., or 
still better below 43° F. A good result may then more 
conj&dently be expected. But the consumption of ice with 
this application of the separator method is of course con- 
siderable. 

In this connection I want to call attention to a bad 
practice v;hich is followed at some creameries where the 
cream is heated to 167°-176° F. In order that the con- 
sumption of ice be not excessive, the warm cream-can is 
left to cool slowly in a cooling tank filled with cold water. 
This cooling, however, takes place too slowly. If good 
coolers are not at hand, it is absolutely necessary to cool 
the cream in tanks filled with iced water, the cream being 
stirred all the time so that the cooling may take place 
through the entire quantity. The method of cooling 
the cream in the open air is not to be recommended, as ii) 
this manner it may easily be infected by dust and bac- 
teria. 

Many different kinds of apparatus for cooling the cream 
are found. The Lawrence cooler (see p. 64, Fig. 20) is 
not very practical for this purpose, the cooling progress- 
ing too slowly. The coolers working in connection with 
the pasteurizing apparatus to be mentioned in next chapter 



190 MODERN DAIRY PRACTICE. 

seem preferable. Fig. 26 shows a Danish cooler which 
j^^ offers a large surface for the cooling. In 

j--^^^^i^ using this apparatus the cream is poured 
g; "^-^ into the reservoir A, the bottom of which 
'g "^-'^ B is provided with several holes through 
^^^^ffi^ which the cream is conducted in a thin 
W^^^ layer over the cooling cylinder B. The 
^■m cooled cream is gathered in the basin C, 
11 and removed from it through the faucet 
L^ i.|.._ D- The water used for cooling is con- 
'^^^C ducted into the cylinder at B, and circu- 
FiG. 36. lates through the spirals. 

Pasteurization of Cream. — Considering the second of 
the measures mentioned for checking bacterial develop- 
ment in tlie newly-separated cream, viz., pasteurization, 
we note first of all that this operation must be conducted 
so that the butter made from the cream does not assume a 
cooked taste. For this reason the pasteurization must be 
made with special precautions. To avoid the cooked taste 
in butter it is often directed not to heat the milk above 
150°-158° F., but in this way the power of pasteurization 
to destroy bacteria is in no small degree diminished. 
According to my experiments we may safely heat the cream 
to 165°-176° F. (75°-80° C), provided either rapid and 
strong cooling is practised immediately after the pasteuri- 
zation, or the cream ripened in a proper manner. I shall 
later on describe the latter method. 

As regards the rapid cooling of cream, my experiments 
have shown that the cooked taste does not seem to reap- 
pear in the butter if the cream is cooled to 39° F. im- 
mediately after pasteurization. It may again be warmed 
to the temperature of ripening immediately after the 



SEPAEATOR CREAM. 191 

pasteurization; an intense cooling seems to be the main 
point. 

The cooling is beneficial in another respect as well, viz., 
in preventing the bacteria of the cream from developing. 
Here we again meet the same conditions as recently at the 
separation. The pasteurization does not kill all bacteria 
in the cream, nor is the separation able to remove all 
bacteria from the same; it is therefore in both cases 
equally important to prevent the bacteria remaining after 
the operations from developing. I must also emphasize 
that heating, as far as the keeping quality of the cream goes, 
has proved of but little benefit if not followed by rapid 
and efficient cooling. The pasteurization may be easily 
conducted without expensive apparatus in small or me- 
dium-sized creameries, if only the person to whom the 
operation is entrusted is sufficiently painstaking. There 
are always smaller quantities of cream than of skim-milk in 
creameries, and the latter therefore calls for apparatus of 
larger capacity. In case of pasteurization of cream, on 
the other hand, we may adopt simpler methods, e.g., to 
place the cream can into boiling water, and thus heat the 
cream to the desired temperature. Steam must not be 
conducted directly into the cream, as this will dilute it. 
In the method given the cream ought to be stirred fre- 
quently, as the desired temperature will then be sooner 
reached. This is important, for if the heating is done 
slowly the cream will assume an intense cooked or "beany" 
taste, which will reappear in the butter. A method which 
will secure more rapid heating is to place the cream-can 
in a wooden reservoir whose cover is provided with a hole 
into which the can fits rather snugly. Steam is intro- 
duced in the space between the wood and the can from a 



192 MODERN" DAIRY PRACTICE. 

pipe, and the cream is stirred with a cream spade during 
the operation. This method of heating the cream has 
been employed for more than ten years at several Finnish 
creameries where " Paris butter " is made. 

Special pasteurization apparatus for cream are also 
found in the trade, and the better ones seem to serve the 
purpose very well. As the apparatus used for pasteuriza- 
tion of cream are essentially of the same construction as 
those used for pasteurizing skim milk, we shall here only 
refer to the description of these which will be found in Part 
III of this book. 



PART III. 
SKIM'MILK. 



Befoke considering the factors which influence the 
keeping quality of skim-milk it will be in order to point 
out that there are different kinds of skim-milk of greatly 
differing qualities, and in many respects of different antece- 
dents. These differences are mainly due to the different 
methods of cream separation by which the milk has been 
obtained. 

Skim-milk from Gravity Creaming. 

The skim-milk obtained by the old shallow-setting 
system is already sour when the cream is skimmed off, and 
as a rule it remains sour for a sufficiently long time before 
any other fermentation to all appearances occurs. So 
long as the lactic acid is not too strong in the skim-milk 
the lactic-acid bacteria may thrive there ; but after a time 
their vital force is gradually weakened by the strong 
acidity which they themselves have produced, and to the 
same extent others, especially the butyric-acid bacteria, 
enter into full activity. The latter have up to this point 
only lived a torpor-like existence, but they now grow into 
activity; the pleasantly acidulated taste, which is the best 

193 



194 MODEEN DAIEY PRACTICE. 

quality of the skim milk, is lost and the applicability of the 
milk decreased. 

The length of time in which this milk will keep 
slightly acid varies greatly. I have noticed cases where 
such milk has kept evenly sour for several days, and others 
where it assumed a rancid taste within twenty-four hours. 
The different conditions to which the milk has been pre- 
viously exposed will largely decide how long the sample will 
keep. These conditions exert the same influence on the 
skim-milk as on any other milk, and we find that if the 
new milk has been handled carelessly the skim-milk ob- 
tained from it will possess a very inferior keeping quality. 

The manner in which the sour milk is kept has also 
decided influence on its keeping quality. Proper clean- 
liness must above all be observed; the acidity should not 
be allowed to develop too far. Strong cooling or pasteuri- 
zation need not be applied, but the temperature should be 
kept at a point that will allow the lactic-acid fermentation 
to continue, but not to develop excessively. This seems to 
take place best at 60° F. The lactic-acid bacteria then 
multiply easily (although not as rapidly as at 77° F.), and 
so strongly that they may hold in check the other bacteria 
found in the skim-milk. This is easily accomplished by 
keeping the sour skim-milk in a light room and in not too 
deep pans, and by stirring the milk occasionally. By these 
precautions, and by mixing some sour skim-milk with it 
every day, it is possible to keep such skim-milk of about 
even acidity for several weeks, as I have often seen done. 

In the modern methods of creaming the cream is always 
removed in a sweet condition, and the skim-milk is also as 
a rule sweet. The problem of its keeping quality is there- 
fore entirely different from that of sour skim-milk. In 



SKIM-MILK. 195 

this case we understand the same by the term " keeping 
quality " as in case of new milk, for which reason all that 
has been said in regard to the keeping quality of the latter 
holds good also with sweet skim-milk. 

Different kinds of sweet skim-milk will keep for a 
longer or shorter time according to the method of creaming 
practised and the treatment it receives. The skim-milk 
obtained from the Holstein method is often quite acid, 
although it ought to be sweet. This skimmed milk being 
often "blue-soured" and of poor quality, it cannot be 
expected to keep long, and at farms where the method is 
used the complaint is often made that the skim-milk 
causes the calves to scour. In the Gussander method the 
skim-milk is also reported not to keep well; in the deep 
setting system, on the other hand, it keeps so much the 
better. The skim-milk obtained by the ice method may 
be even model as far as keeping quality goes — i.e., if the 
milk has been properly handled previous to the cream- 
ing and later on has been treated in the dairy according to 
the strict directions of the ice method. We have seen 
that the skim-milk is not deprived of any of its bacteria in 
the ice method; all germs present in the milk before the 
cooling are found in it when they escape the torpor into 
which they are placed through the cooling. By pasteuriz- 
ing the skim-milk the number and vital power of the bac- 
teria found in the same may be diminished, and if it is at 
once properly cooled the advantages thus gained will be 
retained. 

Separator Skim-milk. — The skim-milk offering the best 
guarantee for keeping quality is, however, that obtained by 
the centrifugal method of creaming. Docent Fjord cor- 
rectly stated in a lecture in 1883 that separated milk must 



]96 MODERN DAIRY PRACTICE. 

be considered the " cleanest of all milk." But this purity 
of the separator skim-milk is far greater and more impor- 
tant than he suspected at the time. He gave this opinion 
because he saw the great advantage arising from the 
removal of the microscopic impurities of the milk by 
means of the centrifugal force. It has now further been 
established that separator skim-milk contains fewer bac- 
teria than even the milk from which it was prepared. The 
data given on page 184 give decided evidence on this 
point. Separator skim-milk will, therefore, keep better than 
any other not especially prepared milk. It is furthermore 
more palatable than other skim-milk, since it is purer and 
may be obtained in almost as fresh condition as new milk.* 
The separation may take place directly after the milking, 
and if the skim-milk is cooled immediately after this opera- 
tion it will keep well. 

Pasteurization of Skim-milk. — The keeping quality of 
the separator skim-milk may be further increased by pas- 
teurization and subsequent rapid cooling. These opera- 
tions are especially essential if the milk has become highly 
infected by bacteria in the stable or during the transporta- 
tion. As shown by the table given on page 184 not even 
the separation is sufficient to produce skim-milk poor in 
bacteria, and it is therefore necessary to adopt further pre- 
cautions to maintain the keeping quality of the milk, for 
which purpose pasteurization and cooling are especially 

* Fjord in Tidsskrift foi' Landokonomi, 1883, says: "As regards 
the sweetness of the centrifugal skim-milk it may be taken for 
granted that every housewife will prefer a sweet milk poor in fat for 
a half-soured, richer milk, no matter if the milk is consumed un- 
boiled, or if it is to be previously boiled, by which process the sour 
milk is easily coagulated." 



SKIM-MILK. 



197 



adapted. Our creamery-men ought particularly to note 
this fact, since the milk received by them is often highly 
infected with bacteria. 

If further proof of the importance of pasteurization and 
cooling of the skim-milk is needed I may refer to the 22d 
Report of the Royal Danish Experiment Station. The 
results of lengthy practical investigations in this line, care- 
fully conducted by Mr. A. P. Lunde, are published in this 
excellent report and form a worthy continuation of Fjord's 
experiments. The results present the most striking proof 
of the importance and necessity of increasing the keeping 
quality of skim-milk by the operations mentioned.* 

A short explanation may be in order concerning the 
different pasteurizing apparatus and coolers at present on 

* The following summary of experiments in heating skimmed 
milk to different temperatures and subsequent cooling, conducted by 
Fjord (1884) and Lunde (1890), show that the keeping quality of 
the milk is directly dependent on the degree of heat and of cooling 
applied. The milk was cooled to 12^° C. (54° F.) in the experiments 
of 1884, and to 25° C. (77° F.) in those of 1890. The figures given 
represent the number of hours during which the skim-milk could 
stand boiling. 



Skim-milk 
Cooled to 



1884 
1890. 



No 
Heating 
Applied. 




Skim-milk Heated to 




50° C. 
(122° F.) 


60° C. 
(140° F.) 


65° C. 
(149° F.) 


70° C. 
(158° F.) 


80° C. 
(176° F.) 


90° C. 
(194° F.) 


11.8 
5.0 


17.0 
6.9 


27.8 
20.8 


34.8 
28.0 


37.0 
36.9 


40.4 
38.0 


41.2 
41.6 



12J° C. (54° F.). 
25° C. (77° F.). 



(22d Report Copenhagen Experiment Station, 1891, p. 35). 
Lunde {loe. cit., p. 144) concludes from his numerous experi- 
ments with pasteurization of skimmed milk that its keeping quality 
was only slightly increased by the pasteurization if this was not fol- 
lowed by a cooling. — W. 



198 



MODERN DAIRY PRACTICE. 



the market. This whole question of the treatment of the 
milk being a result of the investigations of late years, the 
apparatus bear in general evidence of being first attempts. 
The pasteurization apparatus most tried in practice at 
the present is doubtless the one constructed by Prof. Fjord 
in Denmark, of which a cut is given below. The milk 




Fig. 27. 
reservoir is of tinned copper and is surrounded by a cover 
of galvanized iron, between which the steam is conducted. 
A stirring apparatus resembling a churn-pole is made to 



SKIM-MILK. 



19^ 




200 



MODERK DAIRY PRACTICE. 



rotate in the milk-cau. This keeps the milk in constant 
motion and jjrevents it from scalding. Fig. 28 shows how 
the apparatus is combined with a separator and a cooler: 
the latter is of a similar construction, as that shown in 



Pig. 26. 



Another pasteurizing apparatus in the trade is that 
manufactured by the Swedish Separator Company in 




Pro. 29. 
Stockholm (Fig. 29). The apparatus consists of two copper 
vessels with double walls and bottom, placed inside of one 
another at a distance of ^-^ of an inch. The milk, which is 
supplied from cup e. is heated between the vessels and let 
out at q. and after finished pasteurization at //. Steam 
enters the vessels through the pipe b, which conducts it to 



SKIM -MILK. 201 

the bottom of both vessels; the condensation water escapes 
at c and d, and after finished pasteurization from I. 

The apparatus is said to work well, is easily cleaned, 
and may easily be combined with a cooler. No stirring 
contrivance is necessary to avoid scalding of the milk, this 
being in motion during the whole heating in a thin layer 
between the two warm surfaces. 

A pasteurization apparatus constructed by Bitter has 
been adopted to some extent in Germany. It consists of a 
cylinder holding about 50 quarts and supplied with a cover; 
a three-centimeter (l|^-inch) worm is placed in the same, 
through which the steam circulates and heats the milk 
in the cylinder, which is stirred by means of a crank. 
Forty quarts of milk may be heated to a temperature of 
167° F. in fourteen minutes. Bitter has also constructed 
hauling-cans which are sterilized from the waste steam 
and afterwards filled directly from the cylinder, or still 
better directly from the cooler. The latter stands in direct 
connection with the pasteurization apparatus, and accord- 
ing to Bitters instructions, ought always to be sterilized 
by steam before being used. 

Besides the three pasteurization apparatus briefly de- 
scribed in the preceding, which represent three different 
types, a large number of others have been constructed dif- 
fering more or less from these. As most of these appa- 
ratus are new and rather untried, it may be safest for the 
time being only to buy them on a guarantee from the man- 
ufacturer or the dealer.* 



*For descriptions and illustrations of other apparatus than 
those here mentioned, see Weigmann, "Milchconservirung," 1893, 
pp. 17-41.— W. 



202 M0DER]S| DAIRY PRACTICE. 

Before leaving this subject it may be well to draw some 
general conclusions from what has been treated in the pre- 
ceding chapter — conclusions which may deserve attention 
also of others than dairymen. 

Skim-milk is used as an article of food in the house- 
hold of nearly every family in tliis country, as well as in 
many public institutions. We often find a prejudice 
against separator skim-milk, however, and it is therefore 
well to inquire whether or not this prejudice is well 
grounded and in harmony with the facts given in the pre- 
ceding. 

Separator skim-milk, as we have seen, differs from 
gravity-process skim-milk in the following points: 

1. It has not been standing for a long time during 
cream separation. 

2. It has lost the disagreeable macroscopic impurities of 
the milk. 

3. It has fewer bacteria than the new milk from which 
it is prepared at the time of separation, and will therefore 
keep better. 

4. If treated in the proper manner after separation it 
will also continue to remain comparatively free from 
bacteria. 

Skim-milk separated by gravity process has, on the 
other hand, the following shortcomings : 

1. It contains the greater portion of the disagreeable 
filth with which it has been mixed in the barn and else- 
where, since straining only frees the milk from the coarsest 
impurities. 

2. It has been exposed to a cream separation lasting 
twelve hours or more, when the bacteria in most dairies 
have had an opportunity to develop. 



SKIM-MILK. 203 

3. Only after pasteurization and subsequent proper 
cooling will this skim-milk reach the high degree of com- 
parative freedom from bacteria possessed by the separator 
skim-milk. 

In view of these conclusions we cannot but consider 
the prejudice against separator skim-milk for human food 
as unfortunate. It is objected that separator skim- milk 
is so entirely void of all fat that it is not fit for human 
food. To this it may be answered that : 

1. Equally poor skim-milk may be obtained by the ice 
method if the milk is left standing for several days. 

3. Kich skim-milk may also, if desired, be obtained by 
means of the centrifuge. 

3. By mixing new milk or cream with poor skim-milk 
any quality of rich skim-milk may be obtained. 

The mere fact that the skim-milk is obtained by the 
gravity methods is no guarantee that it is rich ; it is often 
its macroscopic impurities which produce the impression 
of richness (see p. 139). 



PART IV. 

BUTTER. 



CHAPTER I. 

TREATMENT OF CREAM PREVIOUS TO THE 
CHURNING. 

In describing the treatment of cream preparatory to 
the churning, and in examining the conditions influencing 
the keeping quality of the butter, we note that the 
different methods of cream separation do not produce the 
same kind of cream. We thus distinguish between two 
main groups — the acid cream obtained from the shallow- 
setting system and the sweet cream obtained in the deep 
setting systems. 

It is natural that raw products so different as these two 
kinds of cream demand a radically different treatment, for 
which reason they ought to be treated separately. To 
avoid repetition the treatment of sour cream from the 
shallow-setting system will be explained after the sour 
cream obtained by ripening of sweet cream has been con- 
sidered, and we shall therefore first take up the treatment 
of sweet cream preparatory to churning. 

204 



TREATMENT OF CREAM PREVIOUS TO THE CHURNING. 205 

Sweet-cream Butter. — The treatment which sweet 
cream must undergo depends, first of all, upon how the 
cream and milk from which it was made have been pre- 
viously handled, and on the kind of butter to be produced. 
Different kinds of butter seem to require cream of differ- 
ent quality, and the sweet-cream butter seem to be spe- 
cially particular in this respect. 

The cream used for the manufacture of this kind of 
butter must not have undergone the least decomposition, 
since the most important point in this butter is that its 
taste has not been changed by any acid fermentation in 
the cream or by other processes. Sweet-cream butter is 
the most delicate, and has the poorest keeping quality of 
any kind of butter. In its manufacture the treatment of 
both milk and cream must therefore, more than ever, be 
directed toward checking the growth of the bacteria. The 
main precautions to be taken in the manufacture of sweet- 
cream butter are as follows: rapid removal of the milk 
from the stable where the milking has been done under as 
cleanly conditions as possible ; sterilization of milk vessels ; 
rapid cooling in a light and clean room, or preferably cen- 
trifuging, and subsequent strong cooling toward freezing- 
point (pasteurization cannot be aj^plied, since sweet-cream 
butter easily assumes a cooked taste) ; then rapid heating 
to the temperature of churning, and the most careful 
churning. Even a partial neglect of these precautions 
will tell on the quality of the product in one way or an- 
other. On account of the delicate nature of the sweet- 
cream butter it has not obtained a general sale on the large 
markets. 

Paris Butter. — In the manufacture of " Paris butter " 
or " St. Petersburg butter " we can reach a far better keep- 



206 MODEKJS^ DAIRY PEACTICE. 

ing quality than the sweet-cream butter can ever claim by 
the application of the method adopted in the manufactur- 
ing of heating the cream to 158°-194° F. (70°-90° C), pre- 
ferably to 167°-185" F. (75°-85° C). This is a real and 
thorough pasteurization, and I need not therefore further 
explain the advantages of the system or its manipulation. 
Here it may be pointed out that the pasteurization may be 
conducted very thoroughly; for a cooked taste in the but- 
ter is not objectionable in this case, but is, on the contrary, 
a desideratum. I cannot leave unmentioned that this 
cooked taste enables the butter-maker to hide all kinds 
of faults in the butter arisen through bad treatment in the 
churning or working of the butter, or through careless 
handling of the milk or cream. 

One of the most important conditions in the making of 
this butter is that the cream be efEectively cooled immedi- 
ately after the pasteurization to a temperature below 50" F. 
The butter will then be firm and will keep well. 

In order to get rid of the bacteria more completely, I 
have applied the method of intermittent sterilization (see 
p. 15) for the pasteurization of the cream, heating this two 
or three times to 140°-149° F. (60"-65° C), with cooling 
between eacli heating. The last heating was always con- 
tinued up to 158° F. (70" C). The result was an extraor- 
dinarily well-keeping "Paris butter." When the tempera- 
ture was not raised above 140° F. (60° C.) the first time, 
and only three heatings were made, the butter had a 
normal taste, while if the temperature was raised to 149° 
F. (65° C.) the first time the butter possessed a somewhat 
too pronounced cooked taste. 

Besides improving the keeping quality of the butter 
the pasteurization of the cream is beneficial in killing 



TREATMENT OF CREAM PREVIOUS TO THE CHURNING. 207 

tubercle bacilli as well as other infectious bacteria that may 
be found in it. According to Bang's investigations the 
tubercle bacilli in milk are killed by heating to 176°-185° 
F. (80°-85° C.).* This occurred if the milk was only 
heated up to the last temperature given, and not kept at 
this temperature for any length of time. A temperature 
of 144° F. (62° C.) made the infected milk greatly less 
dangerous, and at 162° F. (72° C.) it generally grew en- 
tirely harmless. This matter is of importance, for Gas- 
perini has directly proved that the butter can contribute 
to the spreading of tuberculosis. Even 122 days after the 
milk was infected with tubercle bacilli the butter made 
from it contained virulent bacilli which killed animals in- 
oculated with it. 

Lafar also found that spores of typhus, cholera, and 
tubercle bacilli would retain their vitality for a sufficiently 
long time in butter to carry these diseases to living beings. 

Sour-cream Butter. — In the manufacture of sour-cream 
butter, other methods than those given must be followed 
in several respects. It is here necessary that a lactic-acid 
fermentation shall have taken place in the cream. 

As is well known, there are two different kinds of sour- 
cream butter in the market, viz., farm (or dairy) butter 
and creamery butter. In case of the former kind the 
lactic-acid fermentation has usually taken place slowly 
during the creaming in shallow wooden pans, while in the 
manufacture of the latter kind all fermentations were 
checked by cooling during the cream separation, and a 
comparatively rapid lactic-acid fermentation was started in 
the cream after the skimming. The lactic-acid fermenta- 

* See foot-note on page 158. 



208 MODEEN DAIEY PKACTICE. 

tion is in the former kind usually caused by bacteria found 
in large numbers on the walls and bottom of the pans^ or 
is started by means of buttermilk, sour milk, and skim- 
milk. No pure cultures are here applied; but the bacteria 
happening to be found in the pans or the milk are given 
full liberty to produce their characteristic fermentations, 
in the hope that the lactic-acid bacteria will be victorious. 
This hope in some cases miscarries — other fermentations 
occurring along with the lactic-acid fermentation, while 
in other cases this planless ripening yields surprisingly 
good results. As before stated, I have thus at several 
farms met with buttermilk obtained after ripening of such 
spontaneously soured cream which proved to contain almost 
exclusively lactic-acid bacteria. 

The reason why these samples of buttermilk contained 
practically j)ure cultures of lactic-acid bacteria doubtless 
lay in the great cleanliness and strict care of which all the 
dairy work at these farms bore witness, as well as in the 
skill with which the creaming and ripening process was 
conducted. I have still oftener met with ice or sep- 
arator creameries where practically pure cultures were 
found in the buttermilk. 

The method used in bacteriological investigations for 
obtaining pure cultures originated with Pasteur, who pub- 
lished his first experiments in this line in 1857. Succes- 
sive inoculations are made of mixtures of bacteria in differ- 
ent samples of the same substratum in order to learn 
which of the bacteria thrive best in the medium at hand. 
If different kinds of bacteria are inoculated in a certain 
medium, the organisms for whom this medium is most 
favorable easily gain the upper hand over the others. 

If a mixture of bacteria, e.g., those found in ripened 



TREATMENT OF CREAM PREVIOUS TO THE CHURNING. 209 

cream — is inoculated into sterilized milk, certain ones will 
soon gain superiority and produce their specific fermenta- 
tion. If some of the soured sample taken when the fer- 
mentation is most active is then inoculated into a new lot 
of sterilized milk and the inoculation repeated in the same 
way, cultures of a certain bacteria are after awhile obtained 
which in most cases may be considered pure. The sub- 
stratum has then offered so favorable conditions of life to 
this kind of bacteria that it has been able to suppress all 
others. In this manner I once obtained a pure culture 
of a lactic-acid bacteria from a very impure sample of 
milk.* 

How do these conditions occcur in practice in the 
ripening cream in shallow pans ? In the first place the 
lactic-acid bacteria are favored in every way in these, milk 
being the most favorable nutritive medium imaginable. 
Secondly, souring material is transferred partly uncon- 
sciously (the wall and bottom of the pan), partly con- 
sciously by addition of sour milk in which the fermentation 
is at its height. It will be seen that there are here many 
points of similarity with the method applied in laboratories 
for production of pure cultures. Conscious infection by 
means of sour milk does not often take place in farm- 
dairying, and is only resorted to when the unconscious 
infection has proved insufficient. I have, however, found 
places in Savolaks where such inoculation of acid bacteria 
has been the rule and was applied almost daily. This in- 
fection in one place occurred by dipping the wooden spoon 
used in skimming the sour-milk pans into the pan con- 



* " Studien ilber die Zersetzungea der Milch," ia FortscJiritte der 
Medicin, 1889, pp. 122, 123. 



210 MODERN DAIRY PRACTICE. 

taining sweet milk.* Thanks to this manner of procedure, 
the souring took place more rapidly. 

In the unconscious infection of fermentation-starters, 
the cause usually lies in the fact that the milk-pans used 
for creaming have not been sufficiently cleaned. The 
result, however, in this case must evidently be more un- 
certain. Strange to say, we rarely find other than lactic- 
acid bacteria in excessive numbers in sour milk at our 
farms. The reason is doubtless that these bacteria are not 
checked as strongly in their development as others, the 
milk-pans being placed outdoors in the sun, dried and 
aired, to which treatment the putrefactive bacteria are 
very especially sensitive. If the pans be thoroughly sun- 
baked they become wholly sterile, as we saw before, and 
the souring of the milk has then to be started by inocula- 
tion with sour milk. 

The inoculated milk is mixed with all kinds of bacteria, 
and the ripening is not therefore always successful. One 
result of this fact is that farm butter is so much poorer 
in winter, when milk is produced in the stable. Com- 
paratively good pure cultures may, however, be obtained 
under the primitive conditions present in the manufac- 
ture of farm butter. If an effort is made to improve 
these conditions by introducing greater cleanliness in 
stable and dairy, and by increasing the knowledge of the 
principles of dairying among farmers, the result ought to 
be still better. If, for instance, the milk is pasteurized 
before being creamed, we should soon find that the soui'ing 
will always take place in a proper manner also in the 
shallow setting system. 

* At farms in Norway this inoculation is often effected by plac- 
ing a little pure sour milk at the bottom of the milk-pans.— W. 



TREATMENT OF CREAM PREVIOUS TO THE CHURNING. 211 

Adding sour buttermilk, etc., to cream is also practised 
in the ripening of cream from modern methods of cream- 
ing; and here it will happen oftener that j)ure cultures of 
a single bacterium are obtained. The better conditions at 
the creameries and dairies using these methods tend to 
bring about this result; and the aijplication of accessories, 
as pasteurization of the cream, etc., would clearly still 
further forward it. 

It is by no means an easy matter to properly conduct 
the ripening of the cream under differing conditions of 
temperature and facilities; it requires great care and 
power of observation as well as a good store of knowledge 
on part of the butter-maker. The ripening of the cream 
has such a decisive influence on the qualities of the butter 
that cream of the best quality may be entirely spoilt by 
careless ripening. But, on the other hand, a proper ripen- 
ing cannot possibly be conducted in cream poorly cared 
for and containing a large number of injurious bacteria. 
The quality of the butter depends more than is generally 
acknowledged on the manner in which the milk, the 
cream, and butter have been treated, and above all, on 
the ripening of the cream. Martens said as early as 
1869 : " Although other conditions, as the winter feeding, 
the pasture, the milk-cellar, etc., greatly influence the qual- 
ity of the butter, these factors very often get the blame 
for faults originating through carelessness in the treat- 
ment." 

The first condition for obtaining a proper ripening ia 
that the raw material shall be good. If the quality of the 
cream is uncertain it is always safest to pasteurize it before 
ripening. If this operation be well done, and the cream 
be rapidly cooled immediately after the pasteurization, the 



212 MODERN DAIRY PRACTICE. 

sour-cream butter will not, as we saw before, have a cooked 
taste. 

The Danish experiments spoken of on page 197 show 
conclusively that pasteurization properly conducted never 
injures or diminishes the fine quality of the butter, but, on 
the other hand, is very beneficial to the same. The butter 
will keep better at the same time, as bad flavors and taste 
are prevented from appearing in it. The yield of butter 
obtained will be somewhat lowered, partly because the 
buttermilk will be richer, partly because the butter will 
contain less water;* but this decrease is in reality insig- 

* As an average of 51 trials with pasteurized and non-pasteurized 
cream, Lunde obtained 3.73 lbs. of butter from 100 lbs. of milk in 
case of ordinary cream, and 3.68 lbs. in case of pasteurized cream, 
or a loss of 1.3 per cent. 

He obtained the following average results as regards the water 
contetit of the butter made by the various processes: 

Normal cream (15 trials) 14.35 per cent. 

Pasteurized cream " 13.74 " 

milk " 13.85 

Normal cream (22 trials) 14. 17 per cent. 

Pasteurized milk " , 13.03 " 

The buttermilk contained on an average for all experiments the 
following percentages of fat: 

Normal cream 38 per cent. 

Cream pasteurized 37 " 

Milk pasteurized 55 " 

See also Berg, Nordisk Mejeri-Tidn, 9, p. 126; Exp. Sta. Record 
5, p. 1025. 

Lunde (23d Report Copenhagen Experiment Station, 1891, p. 110) 
summarizes his work on pasteurization as follows: " If a creamery 
works under normal conditions and makes first-class batter, it will 



TREATMENT OF CKEAM PREVIOUS TO THE CHURNINO. 213 

nificant, esjiecially since a lower water content must be 
considered a direct advantage. The lower percentage of 
water has also in a measure the effect of making this 
butter keep better than butter from non-pasteurized cream. 

The second condition for a good ripening of the cream 
is that the butter-maker shall be well informed on dairy mat 
ters and shall watch the process himself. He should be 
present from the beginning to the end every time the starter 
is prepared; should be present when the ripening of the 
cream is begun; should carefully follow the whole process, 
and when it is done, examine the sourness of the cream. 
Carelessness in the ripening at once stamps the butter- 
maker as incapable. 

Ripening R.oom and Vessels. — To secure a proper ripen- 
ing of the cream the creamery should contain a separate 
ripening-room, as it is otherwise- very difficult to produce 
a good fermentation. In many places the ripening-can 
(or vat) is placed in the separator-room. This practice is 
reprehensible, among other reasons because an even tem- 
perature cannot possibly be maintained there, and neither 
can the atmosphere be kept properly dry; the strict clean- 
lines necessary where the ripening- vat is placed cannot 
possibly be observed in this room. The ripening-room 
should be well isolated from dwelling-rooms and other 
creamery-rooms. It should not be directly connected with 

hardly, according to our experimeuts, pay to iutroduce pasteuriza- 
tion, if a somewhat, higher price than before be not obtained on 
account of the better product. If, on the other hand, a creamery 
has difficulties in making first-class butter, so that the price is always 
discounted because this or that shipment was of inferior quality, 
pasteurization will as a rule be an efficient means of removing the 
trouble and again obtaining the previous price." — W. 



314 MODERN DAIRY TRACTICE. 

the cheese-rooni or curing-rooms, for the fermentation 
processes favored in these are of a wholly different nature 
and inimical to the changes to be brought about in the 
ripening of the cream. It is also evident that the ripen- 
ing-room ought not to serve as a passage-room, and that it 
must be free from draught and equipped so that an ex- 
treme cleanliness may exist throughout. It must be well 
ventilated and kept at an even temperature (from 50°-65" 
F.) The air should be dry, as it is otlierwise very difficult 
to prevent all kinds of fermentation from arising. 

The room must, of course, be provided with large win- 
dows, so that light and sunshine may enter into it. It 
need not be very large and must not be used for any other 
purpose — except, perhaps, for storing of butter ready for 
shipment. 

Wooden cans or tin vats are used for ripening cream. 
At the present the former are most used in Finnish cream- 
eries ; and if manufactured of hard, close-grained oak, they 
may without difficulty be used for some time, as they can 
then be easily and thoroughly cleaned and sterilized; but 
if old and made of soft, loose wood, they have a very 
deleterious influence on the ripening, as they cannot be 
properly cleaned even by steaming, and the result is that 
all kinds of bacteria lodge in them which may give 
rise to faulty ripening. In my opinion the ripening-vats 
prepared from tin, or tinned copper, are always to be pre- 
ferred, as they may easily be kept clean and sterile. Metal 
vessels are sometimes objected to on account of being good 
conductors of heat; but if a proj)er ripening-room the 
temperature of which can be regulated is available, this 
objection will be of no importance. If such a room can- 
not be obtained, an even temperature of the cream may 



TREATMENT OF CREAM PREVIOUS TO THE CHURNING. 215 

easily be obtained by enclosing the ripening- vessel in wood, 
hay mattresses, etc. 

In the creameries of North Germany the ripening 
usually takes place in small tin vessels placed in water- 
basins, the temperature of which is regulated by means 
of steam or ice. In many respects this is a very prac- 
tical method; but it has the disadvantage that a good 
deal of moisture is introduced into the ripening-room, so 
that it becomes very difficult and almost impossible to 
keep the room free from colonies of mold and bacteria. 

The Ripening Process. — In many places abroad — for 
instance in Germany — the contents of the ripening-vat 
are left to sour, without the addition of any starter, as in 
case of the old shallow-setting system. This method 
is, however, too slow and uncertain, and the application of 
a separate acid starter is therefore always to be recom- 
mended. We must carefully watch so that the cream is 
not contaminated or mixed through the starter with a 
fluid containing faulty fermentations. The qualities of 
the starter must therefore be daily tested by taste and 
odor, and the progress of the ripening process be watched 
by repeated careful observations. 

Acid Starter. — At our creameries three different kinds 
of starters are generally used at the present, viz. : (1) hutUr- 
milh from the last churning; (2) ripened cream; (3) hutter- 
milh from another creamery. The well-known Danish 
dairy instructor, Boggild, treated this topic in a lecture de- 
livered in Odense in 1890. The following description and 
discussion of the ripening process is taken from the lecture : 

1. Buttermilh Acid Starter. — " There is no lack of ex- 
amples that older, well-conducted creameries have used 
buttermilk as starter during a series of years; but it would 



21G MODEllN DAIRY PRACTICE. 

be incorrect to conclude from this that such a method of 
procedure is applicable under all conditions, for we have 
learned by experience that ripening faults may be trans- 
ferred from one lot of cream to another by the applica- 
tion of buttermilk, and may even be increasing until 
the method of ripening is changed. The application of 
buttermilk from the previous churning can therefore only 
be recommended as long as the ripening process occurs in 
the proper manner. 

Sour cream from the mess ready for churning is used 
in place of buttermilk in some creameries. This has the 
same advantage and the same danger as the use of butter- 
milk, and is only to be preferred where there is reason to 
suspect that injurious micro-organisms or other impuri- 
ties have been added in the churning or the washing-down 
of the cream. Both buttermilk, cream, or any other kind 
of starter used must be kept at a low temperature from 
the time it is ready and till it is to be used, so that it does 
not become damaged. 

2. Neio Milk Acid Starter. — The application of new 
acid starter is of but recent origin; it was previously 
j)repared from a mixture of water and fresh milk, but 
it is now generally made from cream, fresh milk, or 
partly skimmed milk. A suitable quantity of any of these 
liquids is heated and kept at a temperature most favorable 
to the development of the bacteria desired for the production 
of butter; the result of the application of the new starter 
depends largely on the success obtained in this process. 

The object sought in using a new starter in place of 
buttermilk is to improve the ripening process. It must 
therefore be an invariable rule to examine it carefully as 
to appearance, odor, and taste, and to compare it with the 



TREATMENT OF CREAM PREVIOUS TO THE CHURNING. 217 

buttermilk. If the buttermilk is better than the new 
starter, the former sliould be used. As cream differs from 
milk only in its greater fat content, and as fat does not 
play any part in the nutrition of the lactic-acid bacteria, 
there is no reason to prefer cream for milk as a starter. 
Even if the cream does not give a proper new starter it is 
generally used anyway, as it represents a certain quantity 
of butter, and is not therefore fed to the hogs ; neither is 
it churned separately, but is used as starter on the suppo- 
sition that it is as it ought to be. 

On the basis of experience gained at Danish dairies 
creamery-men are advised always to prepare new starter, 
to compare it with the buttermilk, and to apply the one 
that proves the better. The milk best adapted to prepara- 
tion of starter should be found by comparative trials with 
the milk from different patrons. The patron furnishing 
this milk should then be asked to send the milk from only 
fresh-milking, well-fed cows in a separate can; and this 
should either be sent to the creamery while still warm or 
subjected to a careful cooling on the farm Immediately 
on arrival of the milk at the creamery the butter-maker 
should place it in one or two common cylindrical milk- 
cans previously well cleaned with soda or lime and scalded 
with boiling water ; the milk is then cooled as rapidly as 
possible in ice or cold water. A layer of cream will form 
during the forenoon, and this is then removed with an 
ordinary skimmer and poured into the sweet cream from 
the centrifuge. The partly-skimmed milk is used for 
preparation of starter." The milk is now to be heated, 

*In my opinion separator skim-milk from a well-conducted 
farm is to be preferred for such sweet, partly-skimmed milk. — 
G. G. 



218 MODERN DAIRY PRACTICE. 

which may best be effected by lowering the milk-can into 
hot water, while the milk is continually stirred by means 
of a galvanized-iron rod supplied with a round disk. This 
as well as the milk-can and skimmer must of course have 
been thoroughly cleaned. 

At different places and at different seasons the milk 
must be heated to a temperature of 77°-95° F. (25°-35° C.) 
to become evenly sour in the course of eighteen to twenty 
hours. The exact temperature required is determined by 
experiment. When the correct temperature has been 
reached, the milk-can is carefully placed, so that none of 
the contents is spilled, into a barrel filled with hay. The 
can should be covered with a clean cloth, on which a neat 
hay mattress is put; the milk may now be left alone until 
the next day. As soon as the work begins in the morning 
the butter-maker should examine the starter, for the ripen- 
ing process may be finished. This may conveniently be 
done by placing the vessel in cold water when the milk 
becomes evenly sour. In the majority of creameries it is 
most convenient to have the acid ready at 8 to 10 a.m. 
The upper inch layer of the milk is removed with a skim- 
mer, as it sometimes is less palatable than the rest of the 
acid. The starter is then mixed with the stirring-rod and 
placed in cold water until used. 

The new starter does not usually taste as sour as the 
buttermilk, and a somewhat larger quantity must there- 
fore be used of it. As a disadvantage in the method may 
be mentioned that the souring does not always progress in 
the same manner, so that the butter on separate days of 
even the same week may prove of different quality, while 
an even quality of butter is easily gained by using a butter- 
milk starter. 



TREATMENT OF CREAM PREVIOUS TO THE CHURNING. 219 

The use of a new starter is to be recommended when 
the quality of the butter is deteriorating or is unsatis- 
factory, and above all when milk varying in freshness, 
purity, and general qualities is sent to the creamery. 

Where the quality of the butter is not satisfactory, and 
where it also proves difficult or impossible to prepare good 
new acid, it will be necessary to apply buttermilk from 
another creamery. 

3. Buttermilk from Another Creamery as Starter. — 
This should of course be obtained only from a creamery 
where the butter is good, and where the ripening is suc- 
cessfully conducted at the time. The practice of using 
buttermilk from another creamery is very old, and has 
especially been used in places where proper churning has 
been conducted under great difficulties, and where the 
cream has not soured evenly, but has remained thin and 
turned, bitter and "oflf flavor." However simple this 
remedy may seem it has not often been resorted to — doubt- 
less because butter-makers have considered it a reflection 
on their ability not to get out of the difficulty by their 
own efforts. The practice seems, however, now to be more 
generally followed as the great importance of the ripening 
of the cream for the quality of the butter is better under- 
stood. With the experience of late years we may say that 
in some cases it is a sign of ability and care on part of the 
butter-maker rather than the other way, if he tries to ob- 
tain a good starter from another source when his own has 
for a long time proved unsatisfactory. 

It has happened in some cases that a butter-maker has 
succeeded in getting the ripening process in proper order 
by a single application of good buttermilk from another 
creamery — good results having later been obtained by ap- 



220 MODERK DAIRY PRACTICE. 

plying buttermilk from previous churnings; but there are 
plenty of examples that the difficulty is not always as 
easily adjusted, the ripened cream after some days again 
being of the same undesirable quality as before. To coun- 
teract this it has long in all such cases been a universal 
remedy to make a general housecleaning. The ripening- 
vat, churn, and other wooden utensils are carried out in 
the open air for some days; the creamery-rooms are white- 
washed, etc. Tliis method of procedure is doubtless both 
practical, correct, and necessary; but when it proves in- 
sufficient the attention must also be directed toward the 
other side of the subject, and an especially good starter 
must be provided for several days ahead. This may be 
secured by obtaining good buttermilk daily from another 
creamery, but if the distance is too great, a culture of the 
bacteria of the buttermilk obtained may be carefully kept 
and a portion of the same used daily as a starter." 

Pure-culture Acid Starters. — By the preceding meth- 
ods of securing a good acid starter much is, however, left 
at a venture. We do not know to which lactic-acid bac- 
teria the successful outcome is due; and neither are we 
certain if the cream is not infected by injurious bacteria 
from the starter. To avoid this a new method of prepar- 
ing the starter has been introduced in some foreign cream- 
eries during the last couple of years, according to the 
principle which has proved of such great benefit to the 
fermentation industries, notably the brewing industry. 
As long as yeast containing fungi and bacteria of all 
kinds was used in the manufacture of beer there was no 
certainty of a successful fermentation. A yeast fungus 
sometimes obtained the superiority, a bacterium another 
time, and the result was therefore often different from 



TREATMENT OF CEEAM PREVIOUS TO THE CHURNING. 221 

what was wanted; the beer might turn bitter, be "off 
flavor," etc., although the raw products used were of the 
very best quality. Until lately we were placed in the same 
difficulty in the fermentation industry called the manu- 
facture of sour-cream butter. The comjiosition of the 
starter used is not known, and it perhaps contains a large 
number of injurious bacteria. Although the quality of 
the cream was excellent, a bitter, oily, turnipy or other 
kinds of diseased butter may have been obtained owing to 
the introduction of injurious bacteria into the cream from 
the starter. The effort has perhaps been made to produce 
good milk, to handle it properly throughout, to take good 
care of it during the transportation to the creamery, to 
care for it there according to all the rules of the art, to cool, 
separate and pasteurize it — a relatively germ-free cream 
being thus obtained; and after all this the delicate product 
is calmly mixed with a fluid the qualities of which are 
only partially known, and all preceding efforts may thus 
be overthrown. By a good deal of practice and experi- 
ence the ripening may certainly be successfully conducted 
in this way. A Danish butter-maker has thus, as I recently 
learned, been using the same kind of starter for fourteen 
years without having ever had a faulty ripening. In the 
same way experienced brewers were able to make good 
beer also before the introduction of pure cultures; but 
there could be no certainty of a good, uniform, and well- 
keeping product until the adoption of the latter process. 

Butter-makers cannot prepare such a starter them- 
selves, however, but are obliged to turn to a bacteriological 
laboratory that can furnish them with pure cultures of 
lactic-acid bacteria. We shall return to the pure cultures 
of these bacteria at the end of this chapter in connection 



222 MODERN DAIRY PRACTICE. 

with a further description of the nature and character- 
istics of the different lactic-acid bacteria. 

The methods of applying these pure cultures in the 
creamery business were vague and uncertain until of late; 
the solution of the problem was only a couple of years 
ago in its first stage of development. 

Storch (Copenhagen) recommends the following method 
of procedure for the application of pure cultures : " The 
starter is to be prepared daily by means of a pure 
culture; the latter may best be supplied to the creamery 
in especially-arranged vessels, from which it may be 
drawn in small portions without danger of contamination ; 
the creamery-man adds a sufficient quantity to as much 
new milk (or perhaps preferably separator skim-milk) as 
the creamery is in the habit of using for a starter. Before 
adding the pure culture the milk is heated above 158° F., 
and at once cooled to the temperature at which the ripen- 
ing will take place safest and quickest. It is possible that 
another heating of the milk to 158° F. after a day's in- 
terval will be found necessary. When sufficiently acid 
and completely curdled this milk is ready to be used as a 
starter." 

Weigmann (Kiel) gives the following method : " The 
pure culture is to be ordered from a bacteriological labora- 
tory; full-skimmed separator skim-milk is used in prepar- 
ing the starter. The bacteria found in the same are 
weakened or partially destroyed by cooling or heating; if 
cooling be applied it must be very effective (37°-30° F.). It 
is, however, better to heat the milk to 140° F., cooling it at 
once afterwards to 68°-77° F. A portion of the pure culture 
is then added, at the same time stirring the milk carefully. 
The starter will be ready the following day, and should be 



TREATMENT OF CKEAM PREVIOUS TO THE CHURNING. 223 

renewed every day by adding sweet skim-milk. When a 
disease of the butter is being fought, pure cultures must 
for some time be applied every day for preparing the 
starter; otherwise a fortnightly application of pure cultures 
will suffice." 

In my latest experiments with pure cultures in practical 
dairying I have used the following method of procedure : 
Morning milk from a well-kept farm was separated as soon 
as it came to the creamery. Part of the skim-milk obtained 
was carefully pasteurized;* then cooled to 77°-82° F. (25°- 
28° C), and the pure culture added. The temperature was 
not lowered below 68° F., and the milk, which was covered 
by a clean cloth during the whole time, was therefore 
curdled as early as the afternoon of the same day. The 
cream separated in the morning was pasteurized (at 158° F.) 
and cooled to about 39° F. It was kept at this low tem- 
perature for at least six hours; but perferably until the 
evening, being occasionally stirred. At about 6 p.m. it was 
heated to 73° F., the starter was added, and the cream-can 
then kept wrapped in a hay mattress at ordinary room 
temperature (64° F.). The cream was stirred at least twice 
during the evening, with an hour's interval. It was usually 
properly acid and uniform the next forenoon, and after 
some cooling was poured into the churn. f 

*Thi3 milk may safely be heated to 185°-194'' F. (85°-90°C.). 
Evea if the starter has a cooked taste, the cream ripened by it will 
not according to my experience have this taste unless extraordinarily 
large proportions of starter are used. 

fThe starter used by C. O. Jensen in his experiments was pre- 
pared in the following manner, according to his own description : 
"200-600 cc. (about 7-20 oz.) of milk was drawn from the cow, 
the udder and teats having been washed with a corrosive-sublimate 
solution (1.1000) ; the teats were then wiped with a sieauied towel, 



224 MODEEN DAIRY PRACTICE. 

The question of how ofteu the new starter should be 
prepared from the j)ure culture cannot as a matter of 
course be answered so as to apply to all conditions, as these 
vary greatly at different creameries. The only rule that can 
be given on this point is to use it as often as it proves 
necessary. The new starter is propagated in the usual 
way, separated and pasteurized skim -milk obtained from 
new milk drawn and treated throughout with the most 
minute care being always used. 

The new starter must be watched to prevent the fer- 
mentation from proceeding too far, lest the acidity grow too 
strong for the lactic-acid bacteria, thereby offering other bac- 
teria — e.g., the butyric-acid starters — favorable conditions 
of life. According to my experiments this stage will occur 
when the cream contains about .85 per cent of lactic acid — 
a degree of acidity which but slightly exceeds that usually 

and my hands were also washed with sublimate solution and wiped. 
The milk was drawn directly into a sterile flask provided with a 
cotton plug, through which a piece of glass tubing about one half 
inch wide and three to four inches long was placed ; the latter was 
also closed with a small cotton plug. This plug was removed in 
milking, and the narrow tube was after the milking again closed with 
the plug. As a still further precaution this milk was heated in the 
flask up to 158° F. (70° C.) for ten minutes and rapidly cooled to 
about 77° F. (25° C.)- The seeding with the lactic-acid bacteria was 
done by introducing a recently-ignited capillary glass tube into the 
agar-agar culture and placing it in the milk through the glass tube in 
the cotton plug. Treated with suflficient care the milk was never con- 
taminated, which fact was always directly ascertained. The inocu- 
lated milk was left standing at 77° F. (25° C), and always soured 
evenly in the course of 16-20 hours. From this soured milk agar- 
gelatine cultures were made, which in their turn were used the next 
day for preparing the new starter. 



TREATMENT OF CREAM PREVIOUS TO THE CHURNING. 225 

found in buttermilk. 0. 0. Jensen states that the lactic- 
acid bacteria even succumb at about .75 per cent acidity. 
Too sour starters may therefore cause a great deal of 
damage — first of all because injurious bacteria have been 
allowed to multiply in them. When these reach the cream 
they are again placed under unfavorable conditions, but even 
if they are not allowed to multiply there to any appreciable 
extent they will be present in relatively large numbers and 
go over into the small gatherings of liquids in the butter. 
The acidity will easily increase farther and butyric-acid 
bacteria, if present, will start their fermentation — rancid, 
spoilt butter being the result. Other bacteria, as those of 
"oily butter," may in the same way be propagated from 
the starter to the butter. It is therefore of the greatest 
importance to keep the fermentations in the starter in 
check. No bacteriological analyses or other intricate 
methods are necessary to determine when the starter is 
done and when the fermentation should be stopped by 
cooling. A skilled butter-maker can easily determine the 
question by taste, odor, and appearance of the starter.* 

The proper ripening of the cream is, as has often been 
stated, one of the most difficult problems of dairying, since 
it can very easily fail or be influenced by exterior condi- 
tions. It is above all essential here as everywhere else to 
observe the most minute cleanliness, and to watch all one's 
movements to prevent any possible infection to the cream. 

At many places the cream is run directly from the sep- 
arator into the ripening-vat; but this method is to be re- 
jected, as all kinds of irregularities in the ripening of the 
cream will easily then arise whereby the solidity and grain 

* See foot-note on p. 227. 



226 MODERN DAIRY PRACTICE. 

of the butter may suffer. The cream should be cooled 
strongly and kept for a while at a low temperature. Weig- 
mann gives observations in a similar direction, and is of the 
opinion that such a cooling (for at least four hours) weak- 
ens the vital power of the bacteria in the cream. It is also 
beneficial to keep the temperature of the cream uniform 
by occasional stirrings, thus securing an even ripening and 
removing odors, etc., possibly present in the cream. It is 
of course greatly preferable to pasteurize and then cool the 
cream immediately after the separation. 

The ripening of the cream is usually finished within 
18-20 hours in our creameries. This is called slow ripe^i- 
ing ; the 7' ap id rijyening lasts 6-10 hours. The question 
which of the two is preferable is at the present one of 
the points of dissension in dairying. 

The length of the ripening period depends on (1) the 
quantity of starter used, and (2) the temperature at loliich 
the cream is Tcept. If a high temperature and a large 
quantity of starter be used, the ripening will of course 
take place rapidly. By varying both factors the ripening 
may take place in the time which experience has shown 
the most preferable under the conditions present. The 
duration of the ripening period is in my opinion not so 
important for a successful ripening of the cream as are 
the quality of the cream and the starter, and the degree of 
cleanliness which pervades the whole process. In my first 
pure- culture experiments I used such small quantities of the 
starter that it took thirty-six hours to ripen the cream, and 
a well-keeping, fine butter was obtained ; on the other 
hand, as good and perhaps better may be obtained by a 
short ripening period when the proper precautions are 
preserved. This being the case nothing is gained by a long 



TIIEATMENT OF CREAM PREVIOUS TO THE CHURNING. 227 

ripening, since the time during which the cream may be 
infected with bacteria is thus only increased. 

In rapid ripening greater watchfulness is necessary 
and the progress of the fermentation must be repeatedly 
examined, for the rapidity of the process greatly increases 
the danger of its progressing too far. It may be added 
that if the cream turns too acid, lumps of casein will sepa- 
rate out and later on be taken up by the butter, which will 
then not keep well, casein, as is well known, being very un- 
stable and easily attacked by putrefactive bacteria. AVhen 
ripe for churning, the cream should not contain any sepa- 
rated lumps of casein. 

The cream must not, on the other hand, be ripened too 
little, as the taste will then not be as desired ; the souring 
will continue in the butter and will there take place under 
wholly new conditions, the regulation of which we have 
not in our power. A good acidity, not too mild and not 
too strong, is most desirable for the production of a well- 
keeping butter.* 

* It would be of great advantage to butter-makers, and more 
especially to novices among them, to possess a method by which the 
proper acidity of the cream could be accurately determined. In 
laboratory-work and in investigations conducted by dairy chemists 
the method of titration of the cream by means of an alkali has long 
been practised, but it was not adapted to factory purposes in our 
country until 1890, when Dr. Manns published (Bull. 9, 111. Exp. 
Station) what is known as Manns' Acid Test. The method rests on the 
principle that the compound phenolphtalein gives an intensely red 
color to alkaline solutions ; a solution of an alkali (either potash, soda, 
lime, or baryta may be used) of known strength is added until the 
liquid assumes a permanent red color, and the acidity of the cream can 
then be calculated. The description of the Manns test is given as 
follows : 

Directions for the Use of Manns' Test. — 1. Stir the cream thor- 



228 MODERN DAIRY PRACTICE. 

In case the butter is consumed within a short time a 
mild acidity of the cream may be all right, but if intended 
to be kept for a longer time (as in case of export butter) 
the ripening should be allowed to proceed farther. 

If a good starter made from a pure culture is available, 
a comparatively large quantity may advantageously be used 
to secure a rapid ripening of the cream. This would seem 
especially important in case the cream is poor and impure, 
for the injurious bacteria found in it are then at once 
placed in minority ; a mass infection of the cream is 
started by which means the undesirable forms of bacteria 
are prevented from developing. 

Pure Cultures and Shallow Setting. — It may be of inter- 
est in this connection to examine in how far pure cultures 

oughly ; insert small end of pipette in cream and draw until nearly- 
full ; then put the finger over upper end of pipette and allow cream 
to escape slowly (by admitting air) until mark on neck of pipette is 
reached. Transfer to a tumbler ; rinse the pipette three times with 
lukewarm water, adding the rinsing water to the cream in the tumbler. 
Now add to contents of the tumbler three drops of the solution 
marked " Indicator " (phenolphtalein). 

2. Fill the burette up to the O mark with the solution marked 
" Neutralizer " (alkali solution). 

3. While constantly stirring the cream with the glass rod, allow 
the liquid to flow from the burette into the tumbler until the entire 
contents of the tumbler shows a pink tinge. Stop adding the solu- 
tion from the burette the moment the color is permanent. 

4. Read the level of the liquid remaining in the burette. The 
reading shows the amount of acid present. 

The experience of those using the test indicates that where the 
acidity of the cream is right, to secure the best results in yield and 
flavor of butter from 38 to 42 cc. of the neutralizer will be required 
for the test. It is a simple matter for each butter-maker to learn by 
experiment the exact degree of acidity and churning temperature 
suited to the best results, and with these as standards reduce the 



TREATMENT OF CREAM PREVIOUS TO THE CHURNING. 229 

are applicable in case of the shallow setting system of 
creaming. In experiments in this line I prepared the acid 
starter by means of pnre cultures, in the manner given 
before, added the same to the milk, and found that in this 
way a much more rapid and more certain fermentation 
was obtained than by the ordinary plan. The main condi- 
tion of a successful outcome proved to lie in proper re- 
striction of the fermentation, so that the casein of the 
milk does not coagulate before the creaming was done. 
The butter made kept very well, especially when the milk 
was pasteurized and cooled previously to setting. 

Lactic-acid Bacteria. — A large number of bacteria pos- 

process of butter-making to a certainty. By testing his cream in 
tlie afternoon, the butter-maker will be able to set it to ripen at such 
a temperature that it will show the proper acidity for churning the 
next morning. 

In testing the milk for cheese-making the same directions are to 
be followed, excepting that a much less acid couditiou is required ; 
probably from 15-20 cc. will give the best results. The whole num- 
bers are cubic centimeters ; the intermediate divisions are fractions 
of a cubic centimeter. 

Precautions in Using the Test. — The solution marked "Neutral- 
izer" is prepared of a certain strength. It is essential that this 
strength remain constant. Never let this solution stand without a 
stopper. Keep in glass or stoneware." 

The necessary apparatus and chemicals may be obtained from 
dealers in dairy supplies. Lately Prof. Farringtou has published a 
method of testing the acidity of cream with alkaline tablets of a cer- 
tain strength. For a description of the manner of procedure in ap- 
plying the tablets, see Bull. No. 32, 111. Agr. Experiment Station. 

Concerning the relation of the acidity of the cream to the yield 
of butter, see Sebelien, Landw. Versuchs-Stationen, 34 (1887), p. 
93 ; Manns, Bull. 9, 111. Agr. Experiment Station (1890) ; Wallace, 
Bull. No. 22, Iowa Agr. Experiment Station (1894). 



230 MODERN DAIRY PRACTICE. 

sess the quality of producing lactic acid in the milk ; they 
are able to develoj) at temperatures above 52° F. (11° C.) 
— the optimum temperature as regards their power of fer- 
mentation lying between 82° and 100° F. (28° and 38° C). 
The different bacteria show great differences, however, as 
regards both their optimum temperature and the different 
substances besides lactic acid which they produce in milk. 
The majority of the lactic-acid bacteria are aerobic ; the 
statements made in some text-books to the effect that these 
organisms cannot give rise to regular fermentations in the 
presence of air are therefore erroneous. The advantage of 
stirring the cream during the ripening is apparent from this. 

If the sour milk or cream found in practice is exam- 
ined bacteriologically, we usually find that several differ- 
ent kinds of lactic-acid organisms are active in it at the 
same time, and that neighboring creameries may operate 
with wholly different forms of lactic-acid bacteria. Storch 
also says in his comprehensive and valuable work on the 
"Souring of the Cream": "Every time I obtained new 
samples of butter I received new bacteria. The explana- 
tion that there are no two lots of butter in Denmark pos- 
sessing exactly the same flavor is found in this." 

This is not the place to treat exhaustively the special 
qualities and morphological characteristics of the different 
lactic-acid bacteria.* Some few observations on this point 
may properly be made here, however. All investigations 

* Those studying these questions are referred to the work by V. 
Storch, just mentioned, to the special reports by H. Weigmann in 
Landw. Woclienbl. f. Schleswig-Holstein, to G. Marpmann's article in 
Ergdmungshefte zum Centralhl. f. allgemeine Gesundheitspflege, 1886, 
to C. O. Jensen's bacteriological investigations reported in Bull. 22 
of Copenhagen Arg. Exp. Station, to L. Adametz's researches, a 
summary of which was given at the Agricultural Congress in Vienna, 



TREATMENT OF CREAM PREVIOUS TO THE CHURNING. 231 

have thus shown that cream can be ripened by means 
of carefully-prepared pure cultures in such a manner that 
pure and well-keeping butter is made from it, but that 
there seem special difficulties in obtaining a distinct flavor 
in the butter. Bacteriologists have gone to a great deal of 
trouble in searching for a bacteria which would produce 
not only a strong fresh acid taste, but a good flavor, with 
but little success; so that Spallanzani finally says in de- 
spair that fine flavor and keeping quality are character- 
istics which only to a certain extent go hand in hand, and 
Weigmann doubts that there is any single bacterium possess- 
ing the faculty of bringing about this double end. Jensen 
makes the following demands to a lactic-acid bacterium to 
be used in creameries : (1) that it will sour the cream rather 
strongly in comparatively short time, so that it can com- 
pete with other bacteria present; (2) that it will thrive at 
a relatively low temperature (60°-72° F.); (3) that it will 
coagulate the cream and milk to a uniform homogeneous 
mixture, and give it a slightly sour taste and odor; (4) that 
it will produce an agreeable aromatic taste and flavor. 
But, he adds, we know at the present no acid bacterium 
that fills all these conditions. 

In my experiments along this line I have not, among 
the numerous bacteria examined, been able to show any one 
bacterium possessing all the valuable qualities desired; but 
by cultivating two different organisms, and mixing them 
at the same time in the milk used for a starter, I have suc- 
ceeded in obtaining a starter which produced both good 
acid and an excellent flavor in the cream. I have either 

1890, to "Die Milch " by H. Scholl, 1891, aud to my book on " Sap- 
rophytic Micro-organisms in Cow's Milk " (in Swedish), published 
1889.— G.G. 



232 MODERN DAIRY PRACTICE 

used a short bacterium previously described by me * under 
the name of hacterium acidi lactici as acid-former, or an- 
other longer staff -like bacterium which I have found present 
in many places in our country. Both these organisms 
produce a very marked and pleasant acidity, develop well 
under ordinary creamery conditions, and seem splendidly 
adapted to this object. Neither produce any special flavor 
in the cream or the butter, but do not, on the other hand, 
give undesirable qualities to it. I have obtained flavor by 
the application of either of these bacteria in connection 
with one of the yeast-fungi previously described f as pro- 
ducing both alcohol and lactic acid in milk. This yeast- 
fungus, which I have found in sour and in stringy milk in 
several parts of our country, thrives very well together 
with either of the before-mentioned lactic-acid bacteria. 
By the co-operation of these organisms the cream obtained 
an agreeable acid and flavor, and the butter seemed to 
keep well and was of good taste and flavor. By cultivat- 
ing several distinct bacteria in symbiosis in this way it 
seems that very favorable results may be obtained, if I in- 
terpret rightly the data now at hand. J 

* Fortschritte der Medicin, vol. vii. pp. 124-131. 

f Loc. cit., and p. 107 of this work. 

X Literature on the subject of pure cultures : Storch, " FlOdens 
Syrning" (Ripening of the Cream), 18th Report Copenhagen Experi- 
ment Station, 1890 ; Biedermanri' s Centralblatt, 20, p. 48 ; Weigmann, 
"Use of a Pure Lactic Germ for Ripening Cream," MilcJizeitung, 
1890 and 1892 ; Ldw. TliiereucM, 1891, 527 ; Hyg. RundscJimi, 1892, 
No. 17 ; Adametz and Wilckens, " Souring of Cream by Pure Cult- 
ures of Bacteria," Ldw. JaJirb., 21, p. 131 ; Lafar, " Artificial Sour- 
ing of Cream by Pure Culture," Oest. Ldio. Wochenbl., 1893, Nos. 16 
and 19 ; Klein and Kiihn, " Experiments with Pure Cultures," Der 
Landwirt 1893, No. 53 ; Biederm. Cenlralbl. 1894, p. 459 ; Conn, 
" The Fermentations of Milk," 1892, pp. 67-69 ; Georgeson, " Dairy 
Industry in Denmark," 1893, pp. 44-46.— W. 



TREATMENT OF CREAM PREVIOUS TO THE CHURNING. 233 

Latest Investigations.* — Since the above was written 
(1891) the question of the application of pure cultures in 
the ripening of the cream has taken a great step forward 
so that it now may be safely said that the problem is prac- 
tically solved. Pure cultures that will keep are now in the 
market; they are put up in a practical manner, and as a 
rule contain pure distinct cultures of bacteria. Denmark 
has again taken the lead in this matter, and now furnishes 
an article which is as easily applied as, e.g., rennet extract. 
According to what I have been able to ascertain pure cult- 
ures can be bought in Denmark from not less than three 
firms — Blauenf eldt and Tvede, Copenhagen ; Chr. Hansen, 
Copenhagen; and Quist of Nonneberg. 

Pure cultures inoculated in a fluid were at first intro- 
duced in the trade, but it was impractical both to ship 
and to apply the cultures as put up in vials. Such 
liquid pure cultures do not, on the whole, seem to be able 
to keep very well; they may, however, be applied with ad- 
vantage if they can be used when fresh and are kept under 
favorable conditions; the shape of the vials in which the 
cultures are shipped has also been improved of late. The 
solid pure cultures recently placed on the market are bet- 
ter, especially if the pure culture cannot be secured fresh. 
These can stand being kept for months, even half a year, 
without being appreciably changed in their qualities. 

At the creamery of the Mustiala Dairy Institute, solid 
normal starter from Danish Butter Color Company, Blau- 
enfeldt and Tvede, Copenhagen, is at the present being 
used with great success. In applying it the following di- 
rections given by the manufacturers are followed : 

* Author's addition to the present translation. 



234 MODERN DAIRY PRACTICE. 

1. " Treatment of the Solid Starter as it Comes from 
the Laboratory. — Ten liters of skimmed milk are heated to 
176° F. (80° C), kept for two hours at that temperature, 
and then cooled to 90° F. (32° C). The whole contents 
of the vial are then added and carefully mixed with the 
milk. The milk is placed in warm water, which must be 
kept at the same temperature throughout the souring, and 
the can is covered lightly- — e.g., with cheese-cloth. The milk 
sours evenly after about eighteen hours, when it is cooled 
and left undisturbed until it is to be used. The upper 
layer is skimmed off before using the milk. The starter 
has a pure acid taste; it is somewhat granular, but this 
will entirely disappear during the later treatment. 

2. Treatment of the Starter from Day to Day. — In the 
later treatment a quantity of skim-milk is taken sufficient 
both for the souring of cream and for next day's milk. 
The milk is heated to 176° F. (80° C.) for two hours, then 
cooled to 82° F. (28° C), and a quantity of the starter pre- 
pared the preceding day is added, corresponding to ten per 
cent of the milk (one liter per ten liters). The starter 
should be ready in six to seven hours. It must be carefully 
watched, so that the temperature does not sink below 81° F. 
(27° C.) during the ripening. When the starter is done 
it is at once placed in ice- water, where it is left without 
stirring until it is to be used. The following days we pro- 
ceed in the same manner; a sufficient quantity of skim- 
milk is pasteurized, ten per cent of the preceding days' 
starter is added; and so on until a new pure culture is 
taken. 

The ripening of the cream, churning, and all the other 
work in the creamery are conducted in the ordinary man- 
ner. The temperatures are kept as usual. In the ripen- 



TREATMENT OF CREAM PREVIOUS TO THE CHURNING. 235 

ing of the cream it must be observed that this does not 
turn too sour; this is easily avoided, however, if the cream 
is cooled just wheu the right degree of ripeness is obtained, 
or if the cream is kept somewhat cooler the next time. 

New acid starter ought to be prepared every day instead 
of using buttermilk, as in this manner bacteria are best 
prevented from being introduced by bad milk. How often 
the normal acid starter is to be renewed depends on so 
many conditions — as the care used in preparing the starter 
and in preserving it, the quality of the milk, etc., that it is 
difficult to give any rule; but it may be done from once a 
month to once a week. If it should happen that the 
starter is not good or will not keep, it either comes from lack 
of care in the preparation, or from the fact that the milk 
used is not germ-free, the heating done having not been 
sufficient to kill the bacteria. Private dairies are in such 
cases advised to take the milk from three cows and skim it 
next day, and then treat it as mentioned above. At 
creameries good morning milk from a single patron is 
taken for a starter. If it should happen that starter is 
not ready when needed, owing to milk being too cold, the 
starter is, without being stirred, placed in a vessel with 
water at 77°-81° F. (25°-27° C), according to the season, 
when it will be ready in from one to two hours. In this 
heating process it must be carefully watched, that the 
starter is rapidly cooled as soon as done. 

The best results in using normal acid starter for ripen- 
ing will be obtained when the cream is pasteurized. 

One lot of normal acid starter is sufficient for about 
ten kilos (22 lbs. or a little more than 2i} gals.) of skim- 
milk. The following proportions of cream and starter 
s.hould be observed: 



236 MODERN DAIEY PRACTICE. 

For pasteurized cream, 5-10 per cent. 

For no7i-pasteurized cream at proprietary creameries, 4 
per cent or more. 

For non-pasteurized cream at other creameries, 5 per 
cent or more. All vessels and utensils must be kept care- 
fully clean. ' Normal acid starter ' is kept stoppered, and 
the whole quantity used at once.'^ 

This carefully-prepared method should be strictly fol- 
lowed, even in minute details, if the full benefit is to be 
derived from it. I must particularly warn inexperienced 
persons against " improving the same " or " making it sim- 
pler.^' Only uncertainty is gained thereby, and the real 
benefit is lost. 

It must finally be emphasized, in speaking of pure cult- 
ures as fermentation starters for ripening of cream, that 
in the majority of cases it will hardly pay the trouble of 
applying such if the cream to he ripened he not previously 
pasteurized. The cream may contain so large a number 
of injurious bacteria that the favorable influence of the pure 
culture is greatly diminished and may even be abolished. 
Pasteurization of the cream may be compared with a fallow 
field, in which nearly all weeds are killed, and a good acid 
starter with /,ure and good seed. It is of but little use if 
such seed is sown in a soil full of weed-seeds capable of 
germination; in the same way it is of but little benefit to 
add a pure culture to a cream containing many injurious 
bacteria. The impurities may overpower the good seed, 
and the result will be poor. 



CHAPTEE II. 
THE MANUFACTURE AND HANDLING OF BUTTER. 

The cream having been properly ripened, the cliurn- 
ing may take place. Also during this process it is neces- 
sary to observe all kinds of precautions to protect the 
cream from infection. The churn should as far as possible 
be sterile and should be aired and steamed before being 
used. A very common mistake in creameries is to leave 
the churn standing without cover in an upright position 
when not in use, as it were, to catch all the dust and the 
bacteria slowly settling from the air. Some water will 
usually gather at the bottom of the churn; and with high 
temperatures as a rule reigning in our creameries, we have 
conditions very favorable to bacterial growth, and that in 
the very vessel in which the butter is to be manufactured. 
It will not improve the matter if the cover is always kept 
on the churn, as this will then not properly dry out. The 
churn should be kept upside down when not in use, or if 
movable should be kept out of the way. The temperature 
of the churn should be properly adjusted before the churn- 
ing by rinsing it with recently-melted iced water or boiled 
and subsequently cooled water. If the churn is kept in a 
proper manner, no special sterilization will be necessary 
directly before the churning. 

In order to get through early with the creamery- work, 
the cream is in many places churned and even the butter 

237 



238 MODERN DAIRY PRACTICE. 

worked early in the morning before it is perfectly light. 
This custom ought not to be followed, for it is impossible 
to observe the necessary cleanliness in semi-darkness, and 
to make the necessary and accurate observations without 
which a good churning and working cannot be accom- 
plished. The work should take place in full daylight from 
beginning to end; if the creamery- work thereby extend 
somewhat later it cannot be helped. 

The butter can lose its keeping quality already in the 
churn — above all by the application of a wrong churning 
temperature, so that it cannot be properly freed from the 
buttermilk. The butter granules should remain separate 
and clear at the end of the churning, and the buttermilk 
easily drain from the butter. 

When the butter has come all operations aim at the 
complete removal of the buttermilk particles from the 
butter. As shown by Duclaux, pure butter fat is not a 
nutritive medium for the bacteria; but besides fat, butter 
contains both air and water, as well as buttermilk, with its 
ash materials and albuminoid substance. It is from the 
albuminoids (casein, albumen, etc.) that danger of spoiling 
threatens, for they are especially readily attacked by bac- 
teria and furnish them with the necessary nutrients. The 
importance of diminishing the quantity of buttermilk 
present in the butter is therefore evident; it would doubt- 
less increase the keeping quality of the butter if the butter- 
milk could be entirely removed, but the butter would then 
lose its peculiar flavor and become fat pure and simple. 

The importance of a small bacteria content of the 
buttermilk also follows from what has been said. It is 
intimately mixed with the butter, and forms a favorable 
breeding-place for the fermentation bacteria dangerous to 



THE MANUFACTUKE AND HANDLING OF BUTTER. 239 

the keeping quality and flavor of the butter. The buttermilk 
is nothing but the cream minus the butter, and the maker 
who secures cream of a good quality at the same time 
gains good means of transferring this quality to the butter. 

Influence of Air and Light. — But the keeping quality 
of the butter also depends on other conditions than the 
quality and the amount of buttermilk in it. Duclaux has 
shown through numerous experiments that the butter 
must be protected from the influence of air (oxygen) and 
light. Precautions in this direction should, he says, be 
taken even in the churn — e.g., by washing the butter with 
water poor in oxygen; well-water or spring water should 
be used for washing and not lake or rain water. Duclaux 
considers the latter injurious both on account of their 
larger content of oxygen, as well as the probable presence 
of numerous micro-organisms in them. The advantage 
of the application of ice- water for this purpose has already 
been dwelt on (see p. 136). The butter must farther be 
protected from direct sunlight. 

Some dairymen advocate washing the butter with skim- 
milk; but this practice cannot be recommended, as the 
casein of the skim-milk will be coagulated by the acid 
buttermilk, and cannot be completely removed by subse- 
quent washing and working of the butter. The butter 
may advantageously be washed with ice-water (about 4° C), 
as is done in the making of "Paris butter." The cold 
water will harden the butter granules and favor the ex- 
pulsion of the buttermilk; the butter as a result will con- 
tain less water and less buttermilk. Warmer wash-water 
does not seem to produce the same effect. It is objected 
that the butter is apt to be too hard by this method, but 
this shortcoming can "he remedied in the working. 



240 MODEKN" DAIEY PRACTICE. 

Whether this strong cooling is applicable under all condi- 
tions in the manufacture of sour-cream butter I cannot 
say; the method has proved very satisfactory in the manu- 
facture of " Paris butter." 

The churning should not be stopped too soon ; the but- 
ter granules ought to be well formed before being taken 
out of the churn (about the size of wheat-kernels or 
smaller). In taking the butter out of the churn it is often 
rinsed with water; this method is hardly to be recom- 
mended. It arises from the desire to obtain a mildly-acid 
butter or one entirely free from acidity, resembling some- 
what sweet-cream butter in taste. It frees the butter from 
excessive acid and buttermilk, but the flavor of the butter 
will be apt to suffer at the same time. The ripening may 
therefore rather be conducted so that no excessive acidity 
arises and the churning so arranged that the buttermilk 
drains off without such a washing. 

When the butter is taken out of the churn it is usually 
left in the butter-trough for a while to allow the buttermilk 
to drain off. The butter should here be kept covered to 
prevent dust, etc., from falling into it, and so as not to 
expose it to the action of light. 

Working the Butter. — The butter worker should re- 
peatedly be washed with boiling-hot water before being used 
and then cooled with iced water. It is at present the 
fashion at our creameries to work the butter very lightly the 
first time, so that a good deal of buttermilk is left in it. By 
this method, which springs from a fear of overworking the 
butter, it seems to me, however, that the matter is brought 
over on the wrong track, for the only chance for a com- 
plete separation of unnecessary buttermilk from the butter 
is offered in the first working. In my opinion all pos- 



THE MAKUFACTUKE AND HANDLING OF BUTTER. 241 

sible paius should be taken to make the working thor- 
ough. But the overworking ?— it is objected- " If the 
butter is overworked it will not give off its buttermilk and 
cannot possibly keep well." This is correct, but it is also a 
fact that if the churning has been properly done the first 
working can very well be made so thorough that the 
greater portion of the buttermilk may be removed without 
risking any overworking of the butter. It seems to me 
that it is a confession of lack of ability on the part of the 
butter-maker to say that his butter cannot be properly 
worked the first time without being overworked. Only 
sufficient buttermilk should remain in the butter at the 
first working as is necessary for the solution of the salt. 

Between the workings the butter is kept cooling either 
in tin trays or placed in a cooling-chest, at the bottom and 
cover of which ice is kept. In many creameries I have 
seen colossal refrigerators used for this purpose which it is 
very difficult to air out properly. We therefore find in them 
a disagreeable, sour smell, and their walls are often covered 
with a slimy film of bacteria or all kinds of molds. These 
infectious spots, with which the butter comes in contact, 
must of course be removed. We also find working-troughs 
in some creameries that are of the same kind as the cool- 
ing-chests — too heavy to be carried outside and apt to be 
left to mold in the moist creamery. In many respects 
practical refrigerators introduced at Danish creameries are, 
in my opinion, objectionable for the same reason. 

Salting the Butter. — The butter should not be salted 
too early — i.e., while it still contains a great deal of butter- 
milk. If this is done the effect of the salt to drive out 
superfluous buttermilk is largely lost, the fluid being in 
this case too much diluted. Salt is not added to make up 



242 MODERN DAIRY PRACTICE. 

for the weight lost in the working, but to continue the 
work which this process could not finish. The salting can, 
of course, also be done too late — when the butter is too dry 
or has already been overworked. The salt may increase the 
keeping quality of the butter to some extent.* 

* Some writers argue that the keeping quality of the butter is due 
entirely to the salt which it contains. This assertion is not justified, 
however. While it is well known that salt has strong preserving 
properties it does not generally check the growth of the pathogenic 
(disease-producing) bacteria. The only one of these organisms which 
according to Foster's experiments was influenced by the salt was the 
cholera bacillus. The typhus bacterium was not at all incommoded 
by common salt, and tubercle bacilli only after having been exposed 
to the action of salt for a long time. As regards the non-pathogenic 
bacteria found in milk I have ascertained that they are generally but 
slightly influenced by salt that may be present in the substratum. 
If the conditions are otherwise favorable for these organisms even a 
high salt content in the nutritive solution will not check their devel- 
opment. In the experiments mentioned I grew lactic-acid bacteria, 
among other mediums, in sterilized brine which had previously been 
a preserving fluid for butter. They developed vigorously in it and 
fully retained their ability to produce lactic fermentation, although 
they went through a long series of inoculations from one sample 
tube with sterilized brine to another. If, on the other hand, salt 
was added to this brine so that the solution became saturated, the 
lactic-acid bacteria developed only slowly and feebly and after hav- 
ing been grown in 3 to 4 such solutions, they died out entirely. As 
regards the influence of salt on other bacteria found in milk, I have 
only ascertained that certain putrefactive bacteria are very sensitive 
to the action of salt, while e.g., the butyric-acid bacillus, i.e., the form 
of the same with which I have experimented, is only slightly dis- 
turbed by a high salt content in the substratum. Salt therefore in- 
fluences as a rule only slightly the growth of bacteria. It may be 
noted in this connection that the preserving influence of salt, e.g. in 
butter-making, is largely due to the fact that it indirectly counteracts 



THE MANUFACTURE AND HANDLING OF BUTTER. 343 

Cleaning of Churn. — The buttermilk should be removed 
from the churn as soon as possible after the butter is taken 
up, and the cleaning of the latter should take place at once. 
The churn with cover is washed with cold water and then 
brushed with hot water, after which it is thoroughly 
steamed, or filled one fourth full with boiling-hot water, 
which is churned for five minutes and then drained off. 
The churn and cover is carefully brushed with pure dry 
salt, and rinsed with hot water and aired. This lengthy 
process has proved most satisfactory in practical creamery- 
work. When cleaned in this way the churn will retain a 
sweet smell — which, I am sorry to say, is not often met 
with in the churns of our creameries. 

The butter should be left for some time after salting to 
allow the salt to dissolve. At a temperature of 46°-50° F. 
the butter needs 3-4 hours before the salt is dissolved and 
before the consistency necessary for the last working is 
reached. 

When ready the butter should be firm, of a clear, not 
milky color; should show a dry surface, and when packed 
in the tub should not lose appreciable quantities of brine 
even during a long transport-ation. 

The tub must be properly cleaned and sterilized before 
the butter is packed into it. 

The butter is to be packed closely and firmly in the tub 

the development of bacteria. It leads to unite the small drops of 
buttermilk in the butter to larger, which may be easily expelled in 
working. Unfavorable conditions are thereby created for the bacteria, 
the moisture necessary for their development being removed for the 
larger portion of the butter ; and the salt content where some fluid 
remains becoming so concentrated that the bacteria are checked in 
their development, 



244 MODEKN" DAIRY PRACTICE. 

SO that no air-spaces will appear in it. The rancidity 
seems to start from such interstices, the butter being also 
often discolored in such places. The tub should always be 
packed full of butter ; rather than sending half -filled tubs 
they should be left until next shipment. Neither should 
tubs be sent containing soft butter that has not yet been 
cooled for a sufficiently long time. Such butter cannot 
stand transportation, turns easily off flavor, and suffers great 
shrinkage. There is no harm done if these tubs are left 
till next shipment, if the butter is well made and tubs 
treated according to directions given. 

At most of our creameries the butter when once in the 
tubs is not considered in need of any farther care on part 
of the butter-maker, and it is largely left to its own fate. 
The tubs are \ept in an out-of-the-way place, exposed to 
all kinds of moisture and temperatures. But much is left 
at stake in this way. As before, bacteria must be prevented 
from injuring the butter, and this can most easily be done 
by means of cooling. 

Bacteria in Butter. — When packed a larger or smaller 
number of bacteria is always found in the butter. The 
number will differ according to the treatment which the 
milk received and according to the kind of butter produced. 
In a sample of sweet cream butter examined bacteriologi- 
cally I found a comparatively small number of bacteria an 
hour after it was worked, and the different samples of 
" Paris butter " (see p. 205) analyzed contained still fewer 
such organisms — viz., from 120 to 300 per c.c. As would 
be expected, a far larger number have been found in fresh 
sour-cream butter — viz., not less than 2000-55000 per cc. 
During the first days a perceptible increase in the number 
of bacteria was noticed in all samples of butter, especially 



THE MANUFACTUKE AND HANDLING OF BUTTEE. 245 

in the outer layer. In the centre of the tub a compara- 
tively small increase took place during the first hours, but it 
soon stopped, at least if the butter had been well worked. 
The lively bacterial increase in the surface layer spread 
very slowly toward the centre. 

Lafar (Munich) found an immense number of bacteria 
in sour-cream butter examined by him, which presumably 
had not received the best treatment. In most samples ten 
to twenty million bacteria per gram {-^-g of an ounce) were 
found, and he adds that it is not stretching matters to 
assert that more living organisms are often consumed with 
an ordinary good-sized sandwich than there are inhabitants 
in Europe.* 

The outer layers of fresh sour-cream butter will be 
found to contain a large number of the bacteria that took 
part in the ripening. But these do not generally appear 
to thrive long in butter, unless it is soft and contains 
a good deal of buttermilk. Samples of butter of different 
origin have shown great difference in this respect. If a 
sample is dry and hard, the lactic-acid bacteria and even 
some putrefactive bacteria will soon disappear, so that but- 
ter after four or five days will present an entirely different 
picture to the bacteriologist than before. In place of the 
staff -like bacilli found, other wholly different forms seem 
to appear, such as several kinds of sarcina and small 
micrococci. These forms multiply rapidly, and according 
to what I have been able to find out, do not in general 
exert any bad infliience on the quality of the butter — at 



*Sigismund (Inaug. Dissert. Univ. Halle a. S., 1893) found from 
26,000 to over 2,000,000 bacteria per gram in eight samples of 
Halle butter.— W. 



246 MODERN" DAIRY PRACTICE. 

least when alone. The staff-bacteria have not disappeared 
entirely, but are in a great minority. 

If, on the other hand, a sample of butter is soft and con- 
tains large quantities of buttermilk, the bacilli will retain 
their superiority all the time; the lactic-acid bacteria ap- 
pearing first and later on others, giving rise to more or less 
harmful fermentations. The importance of these condi- 
tions for the keeping quality of the butter is evident without 
any farther elucidation. 

If the butter be cooled, the increase of bacteria spoken 
of will be found to cease very soon. The cooling of the 
butter in tubs takes place very slowly, even if good refrig- 
eration is used, and it seems especially to last long before 
the cooling reaches the centre. My investigations show, 
however, that it is not very important that the cooling act 
on this part of the butter, as no significant bacterial growth 
takes place in the same. Even a slight cooling of the 
butter seems to be of benefit, if it is only sufficiently 
prolonged. Professor Fjord,* who investigated this subject 
found that a cooling to only about 43° F. proved sufficient to 
check the spoiling of the butter; but, says Fjord, " it must be 
remembered that this result could only be reached when 
the butter was cooled from the time it was packed in the 
creamery to within two or three days before the scoring 
took place. If such cooling takes place in practice, both 
creameries and the railroads and the steamers should have 
cooling-rooms for the storage and shipment of the butter.'' 

It is not difficult to arrange for the proper cooling of 
the filled butter-tubs in our creameries. Ice-cellars are 
also found on most farms in our country (butter should 

* See Eighth Report of the Copenhagen Experiment Station, 
" On the Cooling of Butter," 1888. 



THF MANUFACTURE AND HANDLING OF BUTTER. 347 

not, however, be kept in the same room as other articles 
of food). If it is not convenient to keep the butter in 
these, a small room may without much expense be fitted up 
for the purpose in connection with the ice-house. The 
room should be isolated from the heat of the surrounding 
air in the same way as the ice-house, by means of sawdust 
or similar material. It may also be advantageous to renew 
the sawdust every year, or to take it out to be dried, to 
prevent the spreading of fermentation-germs and to de- 
crease its heat-conducting properties, which are increased 
if allowed to grow wet. A Danish cooling-room which I 
saw was adjoining the ice-house, from which two openings 
(about 8 inches square) were made into the cooling-room, 
one near its ceiling, the other near the floor. The cold air 
from the ice-house came in from the lower openiiig, and the 
warmer air from the cooling-room went out above. By this 
arrangement the cooling-room was kept both cool and dry. 

Transportation of Butter. — The butter-tubs must be 
protected against being heated during the transportation 
to the railroad station or steamboat. This is especially 
important where the factory is located at some distance 
from the station. To avoid this heating the butter should not 
be hauled in day-time during the hot season, or else directly 
before shipping, and the hauling-wagons should be provided 
with a double-walled cover, between the walls of which dry 
bran, saw-dust, or powdered charcoal may be packed. 

The refrigerator-cars run on our railroads, and the re- 
frigerator-rooms on steamers, are of the greatest service to 
the butter-producer. The benefit derived from this ar- 
rangement is, however, greatly lessened if the tubs are not 
properly cared for during the 'hauling to and the delivery 
at the station. A reliable driver should do the hauling, 



248 MODERN DAIRY PRACTICE. 

and he should be especially instructed to guard against the 
heating of the tubs. The latter ought not to be taken 
from the wagon too early and should preferably go directly 
from the wagon into the refrigerator-car. 

Extractor Butter. — The extractor butter will contain 
but few bacteria if the milk from which it is made was 
produced under proper conditions of cleanliness. Besides 
the advantages of the separation of the milk, the chances 
of infection of the cream are lessened to the greatest ex- 
tent possible. It is a sad fact, howeyer, that the short- 
comings of the extractor seem to have prevented its general 
applicability up to the present time. It cannot, of course, 
be used for the manufacture of sour-cream butter; the 
sweet-cream butter made by the extractor seems to have a 
tendency to softness and a high buttermilk content. 
" Paris butter " made by means of the extractor from thor- 
oughly pasteurized cream is, on the other hand, in my ex- 
perience, of the highest quality. I have not been in position 
to make any investigation of the keeping qualities of the 
extractor butter. 

The Radiator * is another machine by means of which 
the milk can be made directly into butter (see Fig. 30). It 
is manufactured by Ahtiebolaget Radiator, Stockholm. 
This apparatus, which I have had occasion to test criti- 
cally, has proved considerably better adapted to satisfy 
the demands for good sweet-cream butter possessing 
firmness and good flavor than can the extractor. The 
pasteurized milk is separated at pasteurizing temper- 
ature, by which method a good yield and close sep- 
aration is obtained; the cream is, immediately after the 
separation, cooled in the apparatus to ordinary churning 

* Author's addition to the present translation. 



THE MANUFACTUKE AND HANDLING OF BUTTKR. 249 

temperature, and the cliurning is then conducted by a very 
ingenious arrangement. The fine granular butter which 




Fig. 30. 

drops from the apparatus may easily be worked in the 
ordinary manner. 

Preservation of Butter. — Butter being an expensive and 
very delicate article of food, it has of course been the ob- 
ject of adulteration and admixtures of preservatives. 



250 MODERN" DAIRY PRACTICE. 

Manetti in Milano has made lengthy experiments to 
preserve the butter by exhausting the air from it. It was 
very difficult to apply the method to practical conditions, 
and the butter assumed a spongy consistency, greatly injur- 
ing its commercial value. 

Musso and Manetti in Lodi state that an admixture of 
one gram salicylic acid to one kilogram of butter is able to 
check the butyric-acid fermentation without changing the 
taste and appearance of the butter, and they direct to add 
the acid in washing the butter. According to Bersch a 
salicylic-acid solution of two to three grams salicyclic acid 
per liter is preferable to common water for washing the 
butter. He even recommends keeping the butter in such 
a solution. Boracic acid and borax have also been recom- 
mended for increasing the keeping quality of butter, but 
they seem to give it a bitter taste. 

An admixture of such antiseptics must, however, as 
previously shown (p. 145), be considered an adulteration, 
especially if it takes place without the knowledge of the 
buyer.* 

The salting of the butter is an entirely different matter; 
the fact of its being used is not disclosed for the public, and 
each buyer may easily satisfy himself concerning its pres- 
ence. The great majority of people, moreover, demand salt 
in their butter. [The same applies to the use of butter 
color during the greater portion of the year. — W.] 

Canning Butter. — Eather than applying special anti- 
septics, as salicylic and boracic acid, etc., for the preserva- 
tion of butter, it may be preserved by being hermetically 

* As is the case In ninety-nine cases out of a hundred under 
present conditions. Concerning the admixture of preservatives to 
food articles, see p. 146, foot-note.— W. 



THE MANUFACTURE AND HANDLING OF BUTTER. 251 

sealed — a method which has long been practised, especially 
in case of butter intended for exportation to the tropics. 
Only butter of the very best quality can be used for this 
purpose, as only such will pay for the additional expense 
incurred by this method, and only such butter can stand 
the influence of the long transportation. Both sour- and 
sweet-cream butter are used for canning.* 

* More than four million pounds of this kind of butter was ex- 
ported from Denmark alone during the year 1892-93. — W. 



CHAPTER III. 
DISEASES OF BUTTER. 

It has been and still is a general opinion among dairy- 
men that a great many of the various diseases of butter are 
attributable to a faulty feeding of the cows. But it has 
been proved by bacteriological investigations that many 
diseases are due to an infection of the milk, cream, or but- 
ter with one or more forms of bacteria producing abnormal 
fermentations in the same. The feeding of the cows cer- 
tainly influences the quality of the butter, as has been 
shown in a large number of older experiments. Other 
conditions are also of importance in this regard. Several 
butter faults, like white-specked butter (arising from an 
excess of buttermilk remaining in the butter), or striped 
butter (the salt being unevenly divided), or butter showing 
an uneven color in the tub, etc., arise as a result of faulty 
processes of manufacture. A smoky smell or taste, which 
is sometimes found, especially in butter from small, poorly- 
conducted dairies, is caused by keeping the milk or cream 
in impure air. Wood taste in the butter arises when but- 
ter is kept in tubs either made from an unfit kind of wood 
or not properly cleaned, etc. 

On the other hand, more recent investigations, espe- 
cially by the Danes Storch and Jensen, show that a great 
many of the most common butter diseases have their 
origin in an infection of the milk or cream by all kinds of 
bacteria. 

;352 



DISEASES OF BUTTER. 253 

C. 0. Jensen, who has been very successful in his stud- 
ies of all kinds of butter diseases, separates these diseases 
into two different groups. First, diseases caused by the 
presence of several forms of bacteria, which, each one by 
itself, is harmless. Second, diseases caused by the presence 
of a single definite injurious form of bacteria. 

" Off Flavor " in Butter, — To Group I the butter disease 
characterized by the expression an " off " flavor and taste of 
the butter first of all belong. This disease springs from lack 
of cleanliness in the treatment of the milk and the cream. 
Jensen is correct in stating that the fact that a great many 
forms of bacteria and a multitude of each of them are 
formed during the ripening of the cream is often in itself 
a sufficient reason for the poor quality of butter. A sample 
of butter examined by Jensen, which was described as bitter, 
unclean, dry, and soft, contained an immense number of 
forms of bacteria and many of each form. The disease could 
not be ascribed to any distinct form of bacteria present. 
The numerous foreign bacteria prevented the normal lac- 
tic-acid fermentation, and i is also possible that other 
decompositions arose in the cream by the simultaneous 
presence of so many different bacteria forms than those 
produced by the single bacteria forms themselves. 

Among the diseases of Group II the following have 
been investigated at the present time. 

1. Tallowy Butter. — In his investigations and experi- 
ments as to the ripening of cream Storch found a lactic- 
acid bacterium to which he ascribed the origin of this dis- 
ease. This bacterium is not very different from most other 
lactic-acid bacterium, as far as size and form go; but if al- 
lowed to grow luxuriantly in cream during its ripening it 
will produce a most disagreeable tallowy taste in the butter 



254 MODERN DAIRY PRACTICE, 

made from it, so as to make it unpalatable to the least par- 
ticular palate. 

2. Oily Butter. — This disease is characterized by a 
disagreeable taste and smell in the butter, reminding one 
of ordinary lubricating oils. Faulty methods of working 
the butter or of feeding (as regards the composition or the 
quality of the fodder) are often given as causes. Jensen's 
investigations which are not yet furnished show, however, 
that the disease is caused by a small oval bacterium be- 
longing to the lactic-acid bacteria, which produced a firm 
white coagulum in the milk within 12-24 hours. This at 
the same time assumed a disagreeable, oily odor. The 
bacteria thrived best at about 77° F. (25° C); at ordinary 
room temperature it developed somewhat more slowly. 

3. Root-taste (Turnip-taste). — As is natural, this disease 
was long believed to be due to a too liberal feeding of 
roots; but Jensen has shown conclusively that the ap- 
pearance of disease does not stand in any relation to the 
method or system of feeding, but is caused by one or 
more forms of bacteria which develop in the milk before 
or during the ripening of the cream. In a sample of but- 
ter suffering from this disease, Jensen isolated a staff -like 
bacteria possessing locomotive power; this sample origi- 
nated from cows that were not fed any roots. When the 
bacteria was inoculated into milk or cream it caused " a 
disagreeable, very bitter taste, reminding of turnips or 
rutabagas." 

4. Rotten Taste. — This very troublesome disease was 
mentioned already in the introductory chapter (see p. 20). 
It appeared in 1888 at Dueland and neighboring farms 
(Denmark), and is caused by a bacterium carefully studied 
by Jensen, and by him named bacillus fcetidus lactis. 



DISEASES OF BUTTEE. 255 

According to Jensen's investigations this common dis- 
ease seems to be produced through the activity of sev- 
eral distinct bacteria; first among these a small oval bac- 
teria appearing in groups of two single bacteria. Inocu- 
lated into milk it did not change its appearance, but within 
sixteen to twenty-four hours caused a distinct, somewhat 
sweetish, and at the same time burnt taste and flavor. 

6. Bitter Butter. — This disease seems to be caused by 
several different bacteria. Conn* isolated a micrococcus 
of bitter milk in an American sample of milk; Weigmann 
in Germany speaks of a bacillus of bitter milk which 
causes a bitter butter, but does not injure the cheese made 
from the milk. A third bacterium of a veritable putrefac- 
tive form has in my experiments shown a tendency to 
make both milk and butter bitter. It seems to thrive sur- 
prisingly well in butter; the experiments every time ended 
with the butter practically rotting away. 

7. Dappled Butter. — This disease appears rather fre- 
quently in farm butter during the summer, the butter 
being dappled by grayish, more or less extended, pale 
spots. Danish dairy experience tells us that this condi- 
tion is caused by contamination of the milk in the stable, 
the dairy, or during the milking. This is correct as far as 
the location of the trouble is concerned; but the inner 
cause of the disease seems, according to my investigations, 
to lie in the activity of a bacterium possessing a high loco- 
motory power, which develops in the butter, spreading in 
all directions from small separate centres, thereby giving 
the butter a mottled aiDpearance. It seems to possess a 
smaller vital power the farther it is removed from this 

'''Storr's Agr. Experiment Statiou Report, 1891, p. 158. 



256 MODERN DAIRY PRACTICE. 

center, and the gray color will gradually disappear, nntil it 
is entirely gone. This bacteria will therefore hardly be 
able to spoil larger quantities of butter. Neither is there 
any difficulty in keeping it away from the milk, it being 
unable to stand even a heating to 130° F. 

8. Blue Butter. — This disease has so far only been 
found in Central Europe. It appears in butter made 
from the abnormal milk called bluish milk, and is caused by 
a bacterium [Bacillus cyanogenus).* The Germans Haub- 
ner and Fiirstenberg and the Frenchman Reiset state that 
they have frequently met with such blue butter. Haubner 
says, however, that if the butter was well prepared and 
carefully washed the blue milk would not produce dis- 
eased butter, but only in case of ^ greater quantity of but- 
termilk remaining in the butter. I have also been in 
position to investigate this subject and have corroborated 
Haubner's results. 

9. Moldy Butter. — Butter may assume a moldy taste 
and flavor also in other cases than when very old. I have 
found it in rather fresh butter which had small white 
specks both on its surface and in the inner portion of the 
mass. By microscopic examination the specks proved to 
be mold-fungi. The fungus did not grow on any of the nu- 
tritive substances on hand at that time, so it could not be 
further studied. Segelcke met with moldy, green-colored 
butter in 1879. 

It may be clear from the preceding accounts of the 
main studies and investigations at hand concerning the 
production and keeping of milk and other dairy products 

* See, further, " Saprophytic Micro-organisms in Cow's Milk," p. 63. 



DISEASES OF BUTTER. 257 

that dairying in our days is no more a single trade, but is 
a very complicated industry, requiring intelligent workers, 
not only fully familiar with the manipulations of the 
dairy, but well grounded in their underlying principles. 

The fact alone that the raw material with which we 
have to deal is so delicate and easily changed calls into 
play one's highest efforts of cleanliness; there are so many 
chances of harmful bacterial infection in the various 
manipulations that thoughtfulness, good judgment, and 
well-developed power of observation are essentials for any 
dairyman. 

The demands made on farmers and dairymen as well as 
all dealers in dairy goods for high-quality products have 
greatly increased of late years; more of thorough knowl- 
edge and intelligent understanding is required than ever 
before; automatic work, no matter how faithfully per- 
formed, is no longer in keeping with the greater demands. 
The words spoken by Professor Segelcke more than ten 
years ago are even truer to-day: In dairying the standard 
is constantly being raised higher and higher. 



PAET V * 

CHEESE, 



CHAPTER I. 
BACTERIA AND CHEESE-MAKING. 

Cheese is coagulated and pressed casein which has 
undergone certain processes of fermentation. Without 
fermentations no cheese; without bacteria no fermenta- 
tions; therefore without bacteria no cheese. The bacteria 
make cheese out of the casein and give it the characteristic 
flavor desired in each case. We owe the proof of the cor- 
rectness of these statements to the bacteriological investi- 
gations conducted during late years. Before 1875 it was 
believed that the ripening of the cheese was a chemical 
process. Cohn first maintained that this view was incor- 
rect, and that the ripening is attributable to the vital pro- 
cesses of all kinds of bacteria. Decisive proofs have later 
been furnished by Duclaux, Schaffer, Bondzynski, and by 
Adametz. 

The processes of fermentation which occur in the 

* Author's addition to American translation. 

359 



BACTERIA AND CHEESE-MAKING. 259 

ripening of cheese differ in various kinds of cheese and 
are caused by different forms of micro-organisms. The 
intensity and duration of the fermentations are also differ- 
ent in the various kinds. The soft kinds of cheese undergo 
violent and radical fermentations, while certain kinds of 
English cheese ferment only slightly and very slowly. 
We find a smaller number of bacteria in the latter kinds 
than in the former. Swiss cheese seems to stand nearer 
the soft cheeses as regards the number of bacteria con- 
tained in it and the intensity of the fermentations, but it 
requires a rather long time for perfect ripening. 

What dairy science at the present time knows of the 
bacteriology of cheese-making is due above all to the inves- 
tigations of Duclaux, Adametz, Weigmann, and v. Freu- 
denreich.* The following account is based mainly on the 

* The following references include the main investigations of the 
relation of bacteria to cheese-making published up to date : 
Adametz. Ripening of Emmenthal and Cottage Cheese. Landw. 

Jahrb., 18 (1893), p. 337. 
The Causes of Abnormal Ripening Processes in Cheese. Milch- 

Zeitung, 1891, pp. 837-348 ; 1893, pp. 305-333. 
Baumann. Studies in the Ripening of Cheese. Inaug. Dissert. 

Univ. Konigsberg, 1893 ; Landw. Versuchs.-Siat., 42, pp. 181- 

314 ; £Jxp. Sta. Record, 5, p. 349. 
Benecke. On the Causes of the Changes in Emmenthal Cheese 

during Ripening. Landw. Jahrb., 16, p. 359. 
Conn. Isolation of Rennet from Bacteria-cultures. Storrs School 

Experiment Station Report, 1893, pp. 106-136. 
Duclaux. Manufacture, Ripening, and Diseases of Cantat Cheese. 

Paris, 1878. 

Memoires sur le Lait, I-III. Paris, 1880-84. 

Microbes and Fat. Ann. de I'Inst. Past., 7 (1893), pp. 305-334. 

Freudenreich. Ripening of Emmenthal Cheese. Landw. Jahrb. 

d. Schweiz, 4, p. 17 ; 5, p. 16 ; Centralbl. f. Bakt., 12, p. 335. 



260 MODERN DAIRY PRACTICE. 

results of their researches, and also on original investiga- 
tions by the author. 

In the manufacture of cheese the casein is precipitated 
in two different ways, viz. : 

1. By means of certain bacteria producing a ferment 
which coagulates the casein, or 

2. By means of rennet. 

Fkeudanreich Bacteria causing Formation of Holes in Cheese. 

Aim. d. Microgr. 2 (1890), p. 353. 
The Effect of Excluding Air in the Ripening of Emmenthal 

Cheese. Landw. Jahrb. d. Sehweiz, 6, p. 62 ; Chem. Centr., 1893, 

No. 5. 
Experiments in Preventing the Formation of Holes in Cheese. 

Landw. JaJiri. d. ScJiw., 7, p. 81. 
Causes of Bitter Cheese. FuJiling's Landw. Zeitung, 43 (1894), 

p. 361. 
Graefp. Useful and Injurious Bacteria in the Manufacture of 

Dutch Cheese. Molk.-Zeit., 5, p. 183. 
LePierre. Examination of a Spoilt Cheese. Comptes Rendus, 

1894, p. 476. 
McFadyean. Chem. Bact. Investigation of a Bacterium Causing 

Inflammation of the Udder and Formation of Holes in Cheese, 

Landio. Jahrb. d. 8cJm., 1890, p. 64. 
Malenchini. On Ptomaines in Cheese. Zeitschr. f. Nahrungs- 

mittel Uniers., 7 (1893), p. 7. 
Manetti and Mueso. On the Composition and Ripening of Par- 
mesan Cheese. Landw. Vers. -Stat., 21 (1878), p. 334. 
Pammel. An Aromatic Bacillus of Cheese. Bull. No. 31, Iowa 

Exp. Station. 

Ripening of Cheese. Ibid. 

Weigmann. Formation of Holes in Cheese. Landw. Wochenblattf. 

ScM.-HoL, 1890, p. 890 ; Landw. Jahrb., 20 (1890), suppl. 1. 
Action of Kenuet-producing and Peptonizing Bacteria in the 

Ripening of Cheese. Jahresb. Kiel. Milchw. Inst., 1893; abstr. 

Molk.-Zeit., 7, p. 479. — W. 



BACTEKIA AKD CHEESE-MAKING. 261 

Sour-milk Cheese. — The former method is mainly applied 
in the manufacture of so-called sour-milk cheese (" Dutch 
cheese "), prepared by the spontaneous souring of milk and 
subsequent heating, by which processes the casein is com- 
pletely coagulated. In the making of this cheese the lactic- 
acid bacteria are offered as favorable conditions as possible. 
When the casein is precij^itated the cheese is pressed, and 
it is then often considered ready for consumption. At some 
places the pressed cheese is allowed to ripen for a few days, 
during which time all kinds of fermentations arise. Tlie 
office which the bacteria fill in the manufacture of this cheese 
is then twofold: (1) the casein is precipitated and (2) the 
cheese is ripened by them. In the former work only lactic- 
acid bacteria take part; in the latter such bacteria appear 
as use the casein as fermentation material. The former 
decompose the milk-sugar and precipitate the casein by 
the ferment which they produce; the latter decompose the 
precipitated casein. The latter group of bacteria are 
usually only allowed to develop to a limited extent, there 
being otherwise a danger that the fermentation processes 
will progress too far under the very favorable conditions 
present, iu''which case the bacteria would give rise to harm- 
ful or undesirable fermentations, producing a bad flavor 
and taste in the cheese. This kind of cheese will therefore 
only keep for a short period. 

The sour-milk cheese is the oldest kind of cheese in 
Finland (as in most other dairy countries), and forms an 
important and rich article of food on the table of most 
farmers. Among other kinds of cheese in the making of 
which the lactic-acid bacteria play an important part, may 
be mentioned green Swiss cheese, cottage cheese, etc. 

Cheese Prepared by Means of Rennet. — Considering 



263 MODERN DAIRY PRACTICE. 

next the cheese made by means of rennet, we may first 
mention that rennet forms an animal ferment prepared in 
special glands in the third stomach of calves. In the co- 
agulation of the casein by means of rennet, bacteria as 
it seems, play only an insignificant part.* Eennet acts 
best at 95°-104° F. (35°-45° C). In adding the rennet 
the milk is heated to a higher or lower temperature ac- 
cording to the time in which the coagulation of the milk is 
to take place. 

Among the kinds of cheese belonging to this group we 
may distinguish between two subdivisions: 

1. The firni cheeses, requiring a long ripening period, 
in the curing of which bacteria play the main part. 

2. The soft cheeses, requiring a short period of ripening, 
the curing of which is effected not only by bacteria, but by 
mold fungi. 

The manufacture of the firm cheese is very complicated 
as now practised in cheese-factories; as we shall see, the 
methods followed have been developed from experience. 
Let us take a glance at the various processes in order to 
ascertain what part the bacteria play in these. 

Methods of Manufacture of Firm Cheese. — Milk used in 
the manufacture of full cream cheese is usually recently 
drawn and fresh. Its bacterial content is as a rule rather 
low, but it is of course by far not germ-free. Macroscopic 
as well as microscopic impurities will always be found in 

* The small number of bacteria added in the rennet in proportion 
to those already present in the milk was first called attention to by 
Baumann (Inaug. Dissert. Univ. Konigsberg, 1893). He found that 
under ordinary conditions the rennet added would supply only one 
bacterium for every two thousand already present in the milk. See 
also Pammel, Bull. 21, Iowa Experiment Station, p. 799. — W. 



BACTERIA AND CHEESE-MAKING. 263 

it. Concerning the macroscopic impurities of milk, see 
p. 31. The microscopic impurities are numerous and indi- 
cate contamination of dust or dung-particles in the stable. 
In the making of certain kinds of Dutch cheese it is con- 
sidered of primary importance that the milk be removed 
from the stable as quickly as possible, and that it be coag- 
ulated while still warm from the cow. Those acquainted 
with the care and cleanliness maintained in Dutch stables 
will know that these cheeses are prepared from a compara- 
tively pure milk. 

Rennet and cheese-color are first added to the milk. 
The former coagulates the casein, entangling in it all ma- 
croscopic impurities along with microscopic ones adhering 
to them, and also retaining the bacteria suspended in the 
milk. The bacteria thus inclosed in the coagulated casein 
come from three different sources, viz.: (1) from the milk 
and its impurities; (2) from the rennet — which, especially if 
prepared from calves' stomachs at the cheese-factory, usually 
contains an immense number of bacteria (rennet extract 
contains a small number of bacteria*); and (3) from 
the cheese-vat and the air. In the beginning these bac- 
teria seem to play an insignificant part, and in some 
kinds of cheese the increase takes place but slowly. We 



* The number of bacteria in rennet extract has been determined 
by Baumanu and Pammel. The former (loc. cit.) found in two 
samples of rennet tablets 39,250 bacteria per cc. (strength 1 : 200,000) 
and 32,400 bacteria per cc. (strength 1 : 32,000) ; a sample of Danish 
fluid extract contained 1,407,600 bacteria per cc. (strength 1 : 5000). 
Pammel and students working with him found in five determina- 
tions of the bacteria content of fluid rennet extracts from 409,500 
to 4,019,200 bacteria per cubic centimeter. — W. 



264 MODEEN DAIRY PRACTICE, 

shall see directly, however, that they soon make their pres- 
ence felt. In some kinds of cheese it is considered im- 
portant that the coagulation takes place rather slowly, in 
40 to 50 minutes, and the temperature during the same is 
increased from about 86° to 104°-131° F., a temperature 
especially favorable to certain forms of bacteria. It is 
then cut and run through a curd-mill, and the whey is re- 
moved. 

Some kinds of cheese require that the curd be kept 
warm continually, so that it will rapidly turn acid, by 
which means it assumes a distinct sour taste and flavor; it 
is often also considered advantageous to continue the 
heating even in the press. In this way highly-favorable 
conditions of temperature are for several hours offered the 
bacteria in the curd. There is plenty of moisture, and the 
casein as well as the milk-sugar are excellent nutritive sub- 
stances for bacteria; these therefore multiply rapidly in the 
curd. The action of the bacteria is shown from the fact 
that in nearly all kinds of cheese we observe during the 
first twenty-four hours small holes throughout its mass. 
In some kinds the holes soon disappear; in others they 
remain and sometimes even grow larger. They arise on 
account of a gas generation (especially carbonic-acid gas*) 
caused by certain bacteria, butyric- and lactic-acid bac- 
teria being the main ones. This fermentation generally 
belongs to the normal changes in the cheese. If the de- 
sirable forms of bacteria are not present, or are present in 

• * According to Baumann the gases causing holes in cheese con- 
sist mainly of carbonic acid (63 per cent) and hydrogen, and also 
small quantities of other gases, but no hydrocarbons. {Landw. 
Vers. Stat., 42, p. 214). See also Adametz, Milch-Zeitung, 1893, 
p. 320.— W. 



BACTERIA AND CHEESE-MAKIKG. 265 

too small a number compared with the others, troublesome 
cheese-diseases may arise even in the first stages of the 
manufacture. Freudenreich thus isolated a bacteria which 
caused irregular cracks in Swiss cheese {gehldhter Kdse) 
or else an immense number of irregular holes {Nissler 
Kdse), giving the cheese a different appearance than that 
produced by the desired regular holes. He states that if 
this micro-organism is inoculated into the milk, and cheese 
at once made from it, the comparatively few bacteria will 
cause the appearance of large irregular holes (the first- 
mentioned disease); but if the bacteria are allowed to 
multiply in the milk, i.e., if it is left to coagulate slowly, 
the second form of the disease will arise. 

In some kinds of cheese, e.g. certain English cheese 
where a slow fermentation and a solid, closed cheese is 
wanted, the curd is salted. Besides checking the growth 
of the bacteria this gives to the cheese the salt taste de- 
sired. In other kinds, e.g. Swiss cheese, the first fermen- 
tation is left to continue unchecked, and the salting does 
not take place until the cheese has been pressed. 

Curing of Cheese. — After having been put into molds 
and pressed, the cheese is ready for the curing process in 
which it is to assume the flavor desired. For this purpose 
the cheese is brought either into the curing-room or di- 
rectly into the cheese-cellar, according to the demands in 
each case. The cheese in the former case is allowed to 
dry out somewhat in the fairly dry, pure air of the curing- 
room and is then transferred to the cheese-cellar, where 
the curing proper will take place. The most important 
work which the bacteria have to perform in the cheese 
then begins. 



266 MODERN DAIRY PRACTICE. 

The curing consists of a series of different fermenta- 
tions which succeed one another and are caused by dif- 
ferent kinds of bacteria appearing one after the other. 
Duclaux first gave a scientific account of this phenomenon 
in his in several respects remarkable work on milk entitled 
" Le Lait, Etudes Chimiques et Microbiologiques." In the 
Cantat cheese, manufactured in southern France, he found 
not less than ten different kinds of bacteria during its period 
of curing, seven of which were aerobic and three ana- 
erobic. The statement made of the action of the different 
bacteria is briefly as follows : Some of the bacteria pro- 
duce both a rennet-like substance, the object of which is 
unknown, and a ferment which changes the casein to a 
soft consistency characteristic of the ripe cheese. Other 
bacteria continue the work of the curing and give rise to 
strong-smelling, often sharp fermentation products, which 
finally may be still further changed by other bacteria and 
decomposed into leucin, ammonia, etc. Weigmann has 
also isolated this ferment (casease) and shown its great 
importance in the curing of the cheese. 

Adametz investigated Swiss cheese (Emmenthaler) and 
Swiss cottage cheese {Hmishdse) belonging to the soft 
kinds of cheese to be considered later on, and found in 
them an enormous number of bacteria, of nineteen dif- 
ferent forms, which he refers to three separate groups. 
The bacteria of the first group are not able to dissolve the 
casein, but change it to a characteristic jelly-like consist- 
ency which later is easily attacked by other bacteria and 
subjected to farther changes. Micro-organisms of the 
second group continue where the first group left off and 
are unable to attack the original curd. The bacteria of 



BACTEEIA AND CHEESE-MAKING. 267 

the third group are indifferent. In the curing of the 
Roquefort cheese certain molds play an important part.* 

The number of bacteria contained in cheese increases 
immensely during the curing process. At its beginning 
Adametz found 90,000 bacteria in one gram of Swiss 
cheese, but when the fermentation was at its highest as 
many as 850,000 were found in it. By adding small 
quantities of disinfectants to the cheese, Adametz pre- 
vented the bacteria in the cheese from increasing, but at 
the same time the curing process of the cheese was com- 
pletely checked, t 

Method of Manufacture of Soft Cheese. — In most of 
the firm kinds of cheese spoken of in the preceding, the 
curing process takes place very slowly; in some it lasts for 
a year, in others for several years. In the soft kinds of 
cheese, on the other hand, the curing has a much more 
rapid course. The coagulated and molded curd is highly 
infected by placing the green cheese on straw mats pre- 
viously used, in a room where molds, etc., are plentiful. 
Before long the cheeses will be spotted with brown mold 
colonies which gradually spread to a white downy cover. 
At the same time the bacteria in the cheese have started 
their fermentations, but the relatively low temperature 

* Roquefort cheese is made in the department of Aveyron, 
southern France, from sheep's milk. Carefully-prepared molded 
bread is introduced in the forms between the layers of curd, and 
the cheese is ripened in mountain-caves, where the temperature is 
very low and varies but little (39°-46^ F.), while the air is kept 
exceedingly moist by small streams of water running down the walls 
of the caves (relative humidity about 60°). — W. 

tSee also Pammel (Bulletin No. 21, Iowa Experiment Station, 
p. 798) and Baumann (loe. cit.). — W. 



268 MODERK DAIRY PRACTICE. 

retards their progress, while molds thrive and act ou the 
cheese. After some time the mold vegetation assumes a 
bluish color, and the color of the cheese turns reddish 
yellow. If the air grows too moist, these molds will die 
and the putrefactive bacteria will take their place, thus 
spoiling the cheese. If sunlight strikes the molds, they 
will also die and fermentations are stopped. After some 
time — e.g., with the Camembert cheese in twenty-five days 
— the cheese is brought from the curing-room into the 
cheese- cellar, which is usually built half underground and 
so arranged that its temperature will remain fairly constant 
at 54°-5?° F. (12°-14° C), and that direct sunlight and 
draught are avoided. The activities of the molds are here 
soon checked and the work of the bacteria proper begins. 
These are now in position to multiply immensely. 
Adametz found the usual bacteria content of Swiss cot- 
tage cheese {Hauskdse) 2-5 millions per gram. 

At the present stage of our knowledge of the action of 
bacteria in the curing of cheese it would hardly be advis- 
able to give a more detailed account of the morphology 
and other characteristics of the separate cheese-bacteria 
which have so far been identified. There are still many 
points in the complicated processes of manufacture, and 
especially in the curing of cheese, which are not yet 
worked out, and the nature of several of the bacteria iso- 
lated have not been sufficiently studied in detail. About 
fifty different forms are at the present included among 
the so-called cheese-bacteria, and this number will doubt- 
less be considerably increased when further study has been 
made. In the curing of different kinds of cheese different 
forms of bacteria are evidently at work. Of the ten forms 
of bacteria which Duclaux found active in the curing of 



BACTERIA AND CHEESE-MAKING. 269 

Cantat cheese, not a single form is present in Swiss cheese, 
as shown by Adametz's investigations. In my work with 
Swiss cheese made in Finland I have found but very few 
of the bacteria which the latter scientist gives as typical 
for this cheese. 

All the methods of cheese-manufacture so far described 
are characterized by the fact that although the bacteria 
play a most important part in the making and curing oi" 
the cheese in each case, no special care is taken that the 
desired bacteria are really introduced. It is left to chance 
whether they take part or not. Often, however, the out- 
come is different than was expected, the cheese produced 
having a different flavor and being of a different appear- 
ance than that desired. I shall only mention that the 
Swiss scientist Freudenreich states that 40 per cent of Em~ 
mentlial cheese is not cured in the proj)er manner, and 
that we still more rarely find the correct flavor and taste 
in imitation Swiss cheese. The same is true in case of 
the soft French cheeses. Outside of their native country 
they only exceptionally obtain the genuine flavor and ap- 
pearance. 



CHAPTER II. 
OLD-METHOD CHEESE-MAKING. 

It has always been considered a maxim in dairying 
that the manufacture of cheese differs from butter-making 
in this respect, that while cleanliness is the fundamental 
rule in the latter, it may safely be left out of sight in 
the former. Lack of cleanliness has even by some people 
been considered an essential point in the management of 
cheese-factorieSj and the mountain factories of the Swiss 
have been offered as proof of the correctness of this state- 
ment. Everywhere in these cheese-factories, as I have 
had occasion to personally ascertain, conditions incompati- 
ble with cleanliness are met with, although not to the 
same extent in the large new cheese-factories as in the 
small Alp factories. At the latter the barn usually 
directly adjoins the cheese building; a calf-stable may 
even be found in the cheese building, with calves in it; 
both the walls and the ceiling of the room are black and 
dirty; only dirt floors are usually found, and frequently 
the fireplace lacks a good chimney and the smoke finds 
its way out wherever it can, through cracks in the walls 
and ceiling. Similar conditions are found in the curing- 
room and the intense smell in the latter plainly indicates 
that numerous fermentations take place there. 

Neither is special cleanliness observed in the manufac- 
ture of soft French cheeses, as may easily be ascertained. 

270 



OLD-METHOD CHEESE-MAKING. 271 

Molds thrive luxuriously on the shelves and walls in the 
curing-room, and are not removed therefrom ; no care and 
neatness are observed in the milking and the early treat- 
ment of the milk. And in spite of all lack of cleanliness 
excellent cheese is made. 

In case of English or Dutch cheeses a somewhat dif- 
ferent practice is followed. Cleanliness is observed at 
least in the manufacture of the cheese, although not even 
here is it always considered absolutely essential in order 
to obtain good products. Especially in the curing-room 
or cellar it is often preferred that certain molds attack 
the cheese. 

It may furthermore be noted as characteristic of the 
manufacture of cheese that its theory has only to a small 
extent been worked out. It has been an art in which it 
has been necessary in the main features to blindly " follow 
the steps of our forefathers," without knowing why it is 
done this and not that way. In the manufacture of 
certain kinds of cheese, as, e.g., the Swiss cheese, the 
experience of centuries has accumulated from generation 
to generation. One has not deviated a hair's breadth 
from the paternal inheritance, for otherwise " the cheese 
would not be good." No other explanation was given or 
can be given. 

The old-method cheese-making is in many ways analo- 
gous to the old-method butter-making. In both we act 
according to old custom; in both the fermentations are 
started without knowing their nature or without any cer- 
tainty of the outcome. The fermentations in the former, 
being less radical and far less complicated, are more easily 
reached. In the old-method cheese-manufacture, on the 
other hand, much more complicated processes of fermenta- 



272 MODERN DAIRY PRACTICE. 

tion take place, and we cannot therefore make use of such 
simple means as in butter-making. To reach the desired 
changes in the cheese, it was necessary, where these are 
rather energetic, to give up cleanliness, and a more intense 
infection with fermentation bacteria was thus secured. 
Where less thorough changes are needed, as, e.g., in the 
making of English or Dutch cheeses, greater cleanliness 
can be observed, but cleanliness is not even here observed 
to any similar extent, as we have seen, as is necessary in 
the manufacture of butter. 

It is but natural that successful results are often not 
obtained when, as is often the case, several kinds of cheese 
are made in the same factory and kept in the same curing- 
room. We saw that the different kinds of cheese need 
different bacteria for their proper curing, and different de- 
grees of moisture and temperature, etc., and still they are 
made to cure in the same room and it is expected that 
each will develop its characteristic flavor. The result usu- 
ally is that the different kinds are all failures. 

If we compare such cheese-factories with those in 
Switzerland, we find at once that the old method of cheese- 
manufacture in the latter country is on a considerably 
firmer basis than that elsewhere. Only one kind of 
cheese is usually made in Switzerland, and it has been 
manufactured through centuries. All curing-rooms, cheese- 
factories, and perhaps also farm-houses have been infected 
with the very bacteria favorable to the curing of this 
cheese, and it is therefore almost a certainty that the correct 
bacteria will appear to ripen the cheese in the manner de- 
sired.* In the same way every section of France makes 

* Bauraanu (Landw. Vers. Stat., 42, p. 314) states that the fact 
that genuiue Emmenthal cheese, i.e., such made in SwitzeiUiud it- 



OLD-METHOD CHEESE-MAKING. 273 

mainly one kind of cheese, and it is natural that the bac- 
teria useful in each case under such conditions must 
gradually obtain the upper hand. 

We may in this connection mention a practice which I 
have been informed has been followed at a German cheese- 
factory in order to start the correct fermentation in the 
soft "French cheese." When the factory was opened, 
some green cheese guaranteed to be genuine, was im- 
ported from France. The whole factory was then in- 
fected with this cheese, the cheese-room and the vats, 
the curing-room, cellar, and especially the shelves in the 
rooms, etc. When cheese was later carefully made accord- 
ing to the directions given, the curing process desired, and 
an excellent quality was secured in the product. Such a 
method of mass-infection is a step toward new-method 
cheese-making — toward the cheese-making of the future. 

self, is better than that made elsewhere, is due not so much to the 
aromatic feed which the cows find in the mountain pastures or in a 
higher fat content of the Swiss milk, as to the number of different 
forms of bacteria in the milk being subject to smaller changes, and 
the process of manufacture followed being better suited to the mix- 
ture of bacteria in the milk, than is elsewhere the case. — W. 



CHAPTER III. 

NEW-METHOD CHEESE-MAKING. 

The fact that fermentations will always take place m 
the cheese no matter what the method of manufacture fol- 
lowed, would at first thought seem to indicate that there 
can hardly be any improvement in conducting the cheese- 
making on a systematic basis. " Fermentation-starters are 
found everywhere, and we cannot force forward the fer- 
mentation wanted " — these are the arguments with which 
old-method cheese-makers try to silence the efforts of im- 
provement. Several facts are, however, now known which 
throw a doubt on the correctness of these assertions. The 
example just given of the mass-infection introduced at the 
German cheese -factory shows the possibility of a rational 
system of cheese-making. The same objections were of- 
fered against the use of pure cultures in other fermenta- 
tion industries, and these have here been shown entirely 
feasible. In the making of sour-cream butter the old 
method of spontaneous ripening of the cream had to yield 
to modern methods of using starters or pure cultures, and 
in the manufacture of beer the progress made by the intro- 
duction of modern methods has been equally pronounced. 
We cannot overlook the fact that the manufacture of 
cheese is considerably more complicated than the industries 
just mentioned, but, on the other hand, practical laboratory 

374 



NEW-METHOD CHEESE-MAKING. 275 

experiments have already shown that the case is not hope- 
less. 

Instead of following the method of controlling the fer- 
mentation processes in the cheese through a " mass-infec- 
tion/' another may be practised which leads to a more 
successful result, viz., the introduction of pure cultures, 
the milk being pasteurized and strict cleanliness being ob- 
served throughout the manufacture. The main points in 
this method of manufacture, which we may call new- 
method cheese-making, are considered in the following. 

1. Pure, Clean Milk. — Such milk is obtained through 
a careful observation of the directions given in the early 
part of this work as to cleanliness in the stable and in the 
hauling of the milk, and by pasteurization of the same. 
If the milk has not become highly infected with bacteria 
in the stable, even a slight heating may be of service for 
the annihilation of the bacteria. Freudenreich has by prac- 
tical experiments shown the great benefit of pasteurization 
in the manufacture of cheese. The cheese made from 
pasteurized milk did not cure on account of the small 
number of bacteria contained in it; not until the milk 
was inoculated with certain bacteria could the curing take 
place. The pasteurized milk demands special methods for 
the making of cheese, as cooling after the heating, use of 
larger quantity of rennet extract, etc. 

2. Exclusion of Injurious Infection from the Surround- 
ings. — The main condition for the exclusion of harmful 
infection from the surroundings is cleanliness in the 
factory and in the factory men. If the objects sur- 
rounding the milk are kept suflSciently clean, there will 
be no danger in this direction. There is no need of entire 
exclusion of all infection, as any small number of harmful 



276 MODEKN DAIRY PRACTICE. 

bacteria possibly present in the cheese may easily be over- 
powered by the larger number of bacteria added in the 
direct infection. The milk is coagulated in carefully- 
cleaned vats, and the cutting of the curd, the milking, 
pressing, and other processes in the manufacture take 
place as rapidly and in as cleanly manner as possible. 
The Dutch and English cheese-factories in many respects 
come up to the demands made in the preceding. 

3. Direct Infection. — Experiments have been made by 
several scientists for the preparation of pure cultures for 
curing of cheese, but so far with only partial success. 
The difficulties met with in this case are considerable. 
We do not here have only one or two kinds of bacteria in 
pure cultures, as is the case in the brewing of beer or in 
the manufacture of sour-cream butter, but as the assist- 
ance of several kinds of bacteria are necessary in the mak- 
ing of cheese, we must obtain pure cultures of several forms 
to obtain a proper curing of the cheese. This part of new- 
method cheese-making is yet at the stage of experimenta- 
tion, but the investigations at hand at the present give 
certain hope of the solution of the problem. We shall not 
here go farther into a discussion of this question or explain 
the practical methods for the applications of such pure 
cultures, as these are still not sufficiently worked out, or 
have not yet been subjected to tests in practical operations. 

4. Clean Cheese-cellar. — By cleanliness in the cheese- 
cellar we do not understand the same as is usually meant 
by the work in modern dairying. It is not so much a 
question of having a cellar where no bacteria are found as 
a cellar where only those favorable for the curing of cheese 
are found. To reach this, both disinfection and infection 
must be practised; the former in order to destroy the 



NEW-METHOD CHEESE-MAKING. 277 

harmful bacteria possibly present in the cellar, and the 
latter to introduce the useful ones. 

The new method of cheese-making still lacks a good 
many accessories and is but little tried in practice, but it 
is in several respects beginning to break its way. All 
kinds of publications and specific laboratory experiments 
and even smaller cheese-factory experiments give promise 
that the necessary accessories and methods will not be 
long in coming.* It is also doubtless a fact that definite 
systematic methods of cheese-making are absolutely neces- 



* Detailed accounts of the various kinds of cheese and more or 
less complete directions for their manufacture will be found in the 
following works, which include our best literature on the subject of 
cheese-making : 

Klenze. Handbuch d. Kaserei-Technik. Bremen, 1884. 643 pp. 
Engling. Kleines Handbuch d. prakt. Kaserei. Bremen, 1893. 

253 pp. 
Decker. Cheddar Cheese-making, Madison, Wis., 1893. 118 pp. 
Martiny. Die Milch, II. Danzig, 1871. pp. 300-281. 
Sheldon. Dairy Farming. Cassell& Co., New York and London. 

pp. 196-283. 
Harris. Cheese- and Butter-maker's Handbook. Glasgow, 1885. 

pp. 21-87. 
Fleischmann. Das Molkereiwesen. Braunschweig, 1876. pp. 

735-1027. 

Lehrbuch d. Milch wirtschaft. Bremen, 1893. pp. 175-251. 

KiRCHNER. Handbuch d. Milch wirtschaft. 3d ed. Berlin, 1891. 

pp. 389-501. 
Wagner. Milch, Butter und Ease. Weimar, 1881. pp. 184-291. 
Otto. Die Milch und ihre Produkte. Berlin, 1892. pp. 127-169. 
Ddclaux. Le Lait. Paris, 1887. pp. 63-311. 

Principes de Laiterie. Paris, pp. 269-361. 

Leze. Les Industries du Lait. Paris, 1891. pp. 439-683. 

-W. 



27S MODERN DAIRY PRACTICE. 

sary in our dairy practice. The gi*eat uncertainty in the 
present methods and their varying results makes the manu- 
facture of cheese a risky and expensive industry. By the 
introduction of more rational methods good results will be 
obtained with greater certainty; the cheese will be forced 
into exactly the desired fermentations, thereby decreasing 
the number of unsuccessful cheeses manufactured and 
making the cheese produced both cheaper and of a better 
quality. 



INDEX. 



PAGE 

Abnormal milk 44 

Acid starters, use of, in cream-ripening 215 

Aeration of milk 63 

Airing factory utensils 119 

Amphoteric reaction of milk 45 

Arnold steam sterilizer 16 

Baby- feeding, milk for 159 

Bacilli, definition of 2 

Bacteria, aerobic, definition of 11 

anaerobic, definition of 11 

and air 11, 51 

cheese-making 258 

literature on 259 

disinfectants 11 

heat 9 

light 11 

moisture 9 

chemical reaction necessary for 10 

classification of, found in milk 94 

common forms of, in cows' milk 80 

content of milk, influence of season on 92 

weather on 87 

culture method of investigation of 14, 18 

definition of 2 

distribution of 4 

in centrifugal process 183 

in butter 244 

centrifuge-slime 184 

cheese 267 

279 



280 INDEX. 

PAGE 

Bacteria, in cream 184 

ice 133 

milk 83, 184 

rennet extract 263 

skim-milk , 184 

soil ,.... 129 

water. . . 131 

increase of, in milk 88 

injurious to milk 100 

kinds, not numbers, of most importance 90 

lactic acid, forms of 229 

microscopic examination of 13 

multiplication of, by division 5 

spores 6 

non-pathogenic forms of 7 

number of, in milk 83 

pathogenic forms of 7 

producing lactic fermentation 100, 229 

butyric fermentation 101 

putrefactive 104 

size of 4 

weight of 4 

Bacteriological methods of investigations , 12 

Bacteriology, literature of 12 

Bedding, importance of. 29 

Bovine tuberculosis, American literature of 46 

precautions in cases of 49 

Butter 204 

bacteria in 244 

canning of • • • 250 

diseases of 252 

from extractor 248 

radiator 248 

sour cream 207 

sweet cream , 205 

influence of air and light on 239 

manufacture and handling of 237 

preservation of 249 

saltingof 241 

transportation of 247 



INDEX. 281 

PAGE 

Butter, use of chemicals in preserving 249 

working of 240 

Butyric fermentation, bacteria producing 101 

Canning of butter 250 

Centrifugal process of cream separation, , 181 

, distribution of bacteria in 183 

Cheese 258 

curing of 265 

gases in holes of. 264 

making, bacteria and , 259 

literature on 259 

literature on 277 

new-method 274 

old-method 270 

methods of manufacture 261, 262, 267 

number of bacteria in 267 

Chemicals, use of, for preserving butter 249 

milk 144 

Classification of bacteria found in milk . . . „ 94 

Clean hands, necessity of, in factory work 110 

Cleaning of cows, importance of 36 

Cleanliness in butter and cheese factories 108 

milker. 39 

Clothes of factory hands 109 

change of 109 

Coccus forms of bacteria, definition of 2 

Condensed milk 146 

Cow stables, light in 50 

stalls 34 

Cows, proper time of feeding 53 

Cream. 166 

cooling of 190 

from centrifuges 181 

gravity methods 166 

pasteurization of 215 

ripening of. , 190 

by acid starters 215 

pure cultures 220 

latest investigations regarding 233 



282 INDEX. 

PAGE 

Cream, ripening-room and vessels for 214 

separation, shallow setting system of 166 

modern gravity systems of 175 

centrifugal system of 181 

treatment of, previous to churning 204 

Creamery walls and ceilings 118 

Creameries, use of water in Ill 

Dahl's method of milk sterilization 154 

Delay in centrifuging milk, loss from , 59 

removing milk from stable 58 

setting milk, loss from 59 

Disinfectants for use in factories 126 

' stable 76 

Disinfection of butter and cheese factories 125 

stable 76 

Duelund, milk and butter disease at 20 

Engli-Sinclair method of milk-sterilization 161 

Extractor butter 348 

Factories, admittance to 108 

cleanliness in 108 

disinfection of 125 

drainage from 121 

location of 123 

surroundings * 121 

use of purified water in 136 

water in Ill 

ventilation of 119 

Factory floor 114 

hands, clothes of 109 

odor, cause of Ill 

purposes, water for 127 

Farm dairy, the 124 

Floor in butter and cheese factories 114 

Fermenting foods, dangers of infection from 55 

Grain-raising, relation of, to cleanliness in stable 30 



INDEX. 283 

PAGE 

Ice, bacteria in 133 

value of, to the dairyman 66 

Impurities in milk 31 

Infection of milk during milking 28 

in stable, prevention of 26 

precautions against 28 

sources of, in stable 26 

Inflammation of the udder, milk of cows suffering from 47 

Introductory 1 

Lactic acid bacteria, forms of 229 

fermentation, bacteria causing 100 

Microscopic examination of bacteria 13 

Milk, abnormal '. 44 

aeration of • 63 

amphoteric reaction of , 45 

as drawn from the udder 23 

bacteria in 83 

cans, arrangement for steaming 71 

care of, in private households 141 

condensed 146 

coolers 64 

cooling of 62 

delay in removal of, from stable 58 

depots 141 

diseased 50 

for baby-feeding 159 

city consumption 137 

sanatoriums 159 

from cows suffering from inflammation of the udder 47 

tuberculous cows 45 

hauling of 62 

impurities in 31 

increase in bacterial content of 88 

infection of, during milking 28 

in the stable 26 

micro-organisms in, other than bacteria 106 

mixing evening and morning 68 

pails, care of . . . . • 68 



284 INDEX. 

PAGE 

Milkj pasteurization of 157 

preservation of, by freezing 148 

prevention of infection of, in the stable 26 

sterilization of, by Dabl's metbod 154 

Engli-Sinclair's metbod 161 

Scberff 's metbod 151 

Soxblet's metbod 163 

filtration 148 

beating 150 

straining of ,.... 60 

use of cbemicals for preservation of 144 

vessels, steaming of ....... 71 

use of soda in cleaning 70 

wben to cool , 66 

Milker, cleanliness in tbe '. 39 

Milker's bands, wasb-water for 40 

Milking, manner of , 41 

witb wet bands 41 

Paris butter 205 

Pasteurization apparatus 198 

of cream 190 

influence of, on yield of butter 213 

water content of butter 213 

milk 158 

skim-milk 196 

use of, in creameries 313 

Preservation of butter 249 

Pure air, importance of 53 

Pure cultures, literature on tbe subject of 338 

use of, in cream ripening 220 

sballow-setting system of cream-separation 228 

Putrefactive bacteria 104 

Radiator butter 348 

Rennet 262 

Rennet extract, number of bacteria in 263 

Ripening process, metbods of conducting. 215 

room and vessels • 213 



INDEX. 285 

PAGE 

Sanatoriums, milk for • 159 

ScherfE's method of sterilization of milk 151 

Separation of cream, methods of. 166 

Separator cream 181 

Skim-milk , 193 

pasteurization of 196 

separator, value of 203 

Soda, use of, in cleaning milk- vessels 70 

Sour-cream butter 307 

Soxhlet's method of sterilization of milk 162 

Spirillum forms of bacteria, definition of 2, 4 

Stable, cleaning of, annual 74 

daily., 54 

disinfection of 76 

flooring 33 

whitewashing 75 

Steaming milk- vessels 71 

Sterilization, Arnold's steam cooker for 16 

intermittent 15 

of milk .... 153 

methods of . . 16 

of culture media 15 

milk 144 

methods of 161 

Sweet-cream butter 205 

Tuberculosis, bovine, American literature of 49 

precautions in cases of 46 

Tuberculous cows, milk from 45 

Water for factory purposes 127 

iced, use of 132 

purification of 131 

purified, uses of 136 

sterilization of 132 

Whitewashing of stable 75 



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